Update Flutter engine kernel-loading logic. (flutter/engine#3886)

* Fix Flutter loading from dill files.

* Remove disable of causal async stacks.

* Include mirrors patch files as they are needed for release/profile gen_snapshot

* Free the bytes

* Add FTL_DCHECK

engine/src/flutter/lib/snapshot/BUILD.gn

@@ -364,6 +364,11 @@ generate_vm_patched_sdk("flutter_patched_sdk") {
       processed_gypis.math_runtime_sources,
       "//dart/runtime/lib",
     ],
+    [
+      "mirrors",
+      processed_gypis.mirrors_runtime_sources,
+      "//dart/runtime/lib",
+    ],
     [
       "typed_data",
       processed_gypis.typed_data_runtime_sources,

engine/src/flutter/runtime/dart_controller.cc

@@ -44,7 +44,8 @@ std::string ResolvePath(std::string path) {
 
 }  // namespace
 
-DartController::DartController() : ui_dart_state_(nullptr) {}
+DartController::DartController() : ui_dart_state_(nullptr),
+    kernel_bytes(nullptr), platform_kernel_bytes(nullptr) {}
 
 DartController::~DartController() {
   if (ui_dart_state_) {
@@ -55,6 +56,12 @@ DartController::~DartController() {
     Dart_ShutdownIsolate();  // deletes ui_dart_state_
     ui_dart_state_ = nullptr;
   }
+  if (kernel_bytes) {
+    free(kernel_bytes);
+  }
+  if (platform_kernel_bytes) {
+    free(platform_kernel_bytes);
+  }
 }
 
 bool DartController::SendStartMessage(Dart_Handle root_library) {
@@ -94,10 +101,25 @@ bool DartController::SendStartMessage(Dart_Handle root_library) {
   return LogIfError(result);
 }
 
+static void CopyVectorBytes(const std::vector<uint8_t>& vector,
+    uint8_t*& bytes) {
+  if (bytes) {
+    free(bytes);
+  }
+  bytes = (uint8_t*) malloc(vector.size());
+  memcpy(bytes, vector.data(), vector.size());
+}
+
 tonic::DartErrorHandleType DartController::RunFromKernel(
-    const uint8_t* buffer, size_t size) {
+    const std::vector<uint8_t>& kernel) {
   tonic::DartState::Scope scope(dart_state());
-  Dart_Handle result = Dart_LoadKernel(Dart_ReadKernelBinary(buffer, size));
+  // Copy kernel bytes so they won't go away after we exit this method.
+  // This is needed because original kernel data has to be available
+  // during code execution.
+  CopyVectorBytes(kernel, kernel_bytes);
+
+  Dart_Handle result = Dart_LoadKernel(
+      Dart_ReadKernelBinary(kernel_bytes, kernel.size()));
   LogIfError(result);
   tonic::DartErrorHandleType error = tonic::GetErrorHandleType(result);
   if (SendStartMessage(Dart_RootLibrary())) {
@@ -146,11 +168,28 @@ tonic::DartErrorHandleType DartController::RunFromSource(
 void DartController::CreateIsolateFor(const std::string& script_uri,
                                       const uint8_t* isolate_snapshot_data,
                                       const uint8_t* isolate_snapshot_instr,
+                                      const std::vector<uint8_t>& platform_kernel,
                                       std::unique_ptr<UIDartState> state) {
   char* error = nullptr;
-  Dart_Isolate isolate = Dart_CreateIsolate(
-      script_uri.c_str(), "main", isolate_snapshot_data, isolate_snapshot_instr,
-      nullptr, static_cast<tonic::DartState*>(state.get()), &error);
+
+  Dart_Isolate isolate;
+  if (!platform_kernel.empty()) {
+    // Copy kernel bytes so they won't go away after we exit this method.
+    // This is needed because original kernel data has to be available
+    // during code execution.
+    CopyVectorBytes(platform_kernel, platform_kernel_bytes);
+
+    isolate = Dart_CreateIsolateFromKernel(
+        script_uri.c_str(), "main",
+        Dart_ReadKernelBinary(platform_kernel_bytes, platform_kernel.size()),
+        nullptr /* flags */,
+        static_cast<tonic::DartState*>(state.get()), &error);
+  } else {
+    isolate = Dart_CreateIsolate(
+        script_uri.c_str(), "main", isolate_snapshot_data,
+        isolate_snapshot_instr, nullptr,
+        static_cast<tonic::DartState*>(state.get()), &error);
+  }
   FTL_CHECK(isolate) << error;
   ui_dart_state_ = state.release();
   dart_state()->message_handler().Initialize(blink::Threads::UI());

engine/src/flutter/runtime/dart_controller.h

@@ -6,6 +6,7 @@
 #define FLUTTER_RUNTIME_DART_CONTROLLER_H_
 
 #include <memory>
+#include <vector>
 
 #include "dart/runtime/include/dart_api.h"
 #include "lib/ftl/macros.h"
@@ -19,7 +20,7 @@ class DartController {
   DartController();
   ~DartController();
 
-  tonic::DartErrorHandleType RunFromKernel(const uint8_t* buffer, size_t size);
+  tonic::DartErrorHandleType RunFromKernel(const std::vector<uint8_t>& kernel);
   tonic::DartErrorHandleType RunFromPrecompiledSnapshot();
   tonic::DartErrorHandleType RunFromScriptSnapshot(const uint8_t* buffer,
                                                    size_t size);
@@ -29,6 +30,7 @@ class DartController {
   void CreateIsolateFor(const std::string& script_uri,
                         const uint8_t* isolate_snapshot_data,
                         const uint8_t* isolate_snapshot_instr,
+                        const std::vector<uint8_t>& platform_kernel,
                         std::unique_ptr<UIDartState> ui_dart_state);
 
   UIDartState* dart_state() const { return ui_dart_state_; }
@@ -40,6 +42,15 @@ class DartController {
   // during isolate shutdown.
   UIDartState* ui_dart_state_;
 
+  // Kernel binary image of dart script. This is copied and maintained
+  // for dart script lifespan, so that kernel loading mechanism can
+  // incrementally build the dart objects from it.
+  uint8_t* kernel_bytes;
+  // Kernel binary image of platform core libraries. This is copied and
+  // maintained for dart script lifespan, so that kernel loading mechanism can
+  // incrementally build the dart objects from it.
+  uint8_t* platform_kernel_bytes;
+
   FTL_DISALLOW_COPY_AND_ASSIGN(DartController);
 };
 }

engine/src/flutter/runtime/dart_init.cc

@@ -67,6 +67,7 @@ namespace blink {
 
 const char kKernelAssetKey[] = "kernel_blob.bin";
 const char kSnapshotAssetKey[] = "snapshot_blob.bin";
+const char kPlatformKernelAssetKey[] = "platform.dill";
 
 namespace {
 
@@ -243,6 +244,7 @@ Dart_Isolate IsolateCreateCallback(const char* script_uri,
   // Are we running from a Dart source file?
   const bool running_from_source = StringEndsWith(entry_uri, ".dart");
 
+  void* kernel_platform = nullptr;
   std::vector<uint8_t> kernel_data;
   std::vector<uint8_t> snapshot_data;
   std::string entry_path;
@@ -262,15 +264,25 @@ Dart_Isolate IsolateCreateCallback(const char* script_uri,
               GetUnzipperProviderForPath(std::move(bundle_path)));
       zip_asset_store->GetAsBuffer(kKernelAssetKey, &kernel_data);
       zip_asset_store->GetAsBuffer(kSnapshotAssetKey, &snapshot_data);
+
+      std::vector<uint8_t> platform_data;
+      zip_asset_store->GetAsBuffer(kPlatformKernelAssetKey, &platform_data);
+      if (!platform_data.empty()) {
+        kernel_platform =
+            Dart_ReadKernelBinary(platform_data.data(), platform_data.size());
+        FTL_DCHECK(kernel_platform != NULL);
+      }
     }
   }
 
   UIDartState* parent_dart_state = static_cast<UIDartState*>(callback_data);
   UIDartState* dart_state = parent_dart_state->CreateForChildIsolate();
 
-  Dart_Isolate isolate = Dart_CreateIsolate(
-      script_uri, main, g_default_isolate_snapshot_data,
-      g_default_isolate_snapshot_instructions, nullptr, dart_state, error);
+  Dart_Isolate isolate = kernel_platform != nullptr
+      ? Dart_CreateIsolateFromKernel(script_uri, main, kernel_platform,
+            nullptr /* flags */, dart_state, error)
+      : Dart_CreateIsolate(script_uri, main, g_default_isolate_snapshot_data,
+            g_default_isolate_snapshot_instructions, nullptr, dart_state, error);
   FTL_CHECK(isolate) << error;
   dart_state->SetIsolate(isolate);
   FTL_CHECK(!LogIfError(

engine/src/flutter/runtime/dart_init.h

@@ -20,6 +20,9 @@ extern const char kKernelAssetKey[];
 // Name of the snapshot blob asset within the FLX bundle.
 extern const char kSnapshotAssetKey[];
 
+// Name of the platform kernel blob asset within the FLX bundle.
+extern const char kPlatformKernelAssetKey[];
+
 bool IsRunningPrecompiledCode();
 
 using EmbedderTracingCallback = ftl::Closure;

engine/src/flutter/runtime/runtime_controller.cc

@@ -28,12 +28,14 @@ RuntimeController::~RuntimeController() {}
 
 void RuntimeController::CreateDartController(
     const std::string& script_uri, const uint8_t* isolate_snapshot_data,
-    const uint8_t* isolate_snapshot_instr) {
+    const uint8_t* isolate_snapshot_instr,
+    const std::vector<uint8_t>& platform_kernel) {
   FTL_DCHECK(!dart_controller_);
 
   dart_controller_.reset(new DartController());
   dart_controller_->CreateIsolateFor(
       script_uri, isolate_snapshot_data, isolate_snapshot_instr,
+      platform_kernel,
       std::make_unique<UIDartState>(this, std::make_unique<Window>(this)));
 
   UIDartState* dart_state = dart_controller_->dart_state();

engine/src/flutter/runtime/runtime_controller.h

@@ -28,7 +28,8 @@ class RuntimeController : public WindowClient, public IsolateClient {
 
   void CreateDartController(const std::string& script_uri,
                             const uint8_t* isolate_snapshot_data,
-                            const uint8_t* isolate_snapshot_instr);
+                            const uint8_t* isolate_snapshot_instr,
+                            const std::vector<uint8_t>& kernel_platform);
   DartController* dart_controller() const { return dart_controller_.get(); }
 
   void SetViewportMetrics(const ViewportMetrics& metrics);

engine/src/flutter/shell/common/engine.cc

@@ -181,13 +181,16 @@ void Engine::Init() {
 void Engine::RunBundle(const std::string& bundle_path) {
   TRACE_EVENT0("flutter", "Engine::RunBundle");
   ConfigureAssetBundle(bundle_path);
-  ConfigureRuntime(GetScriptUriFromPath(bundle_path));
+  std::vector<uint8_t> platform_kernel;
+  GetAssetAsBuffer(blink::kPlatformKernelAssetKey, &platform_kernel);
+  ConfigureRuntime(GetScriptUriFromPath(bundle_path), platform_kernel);
+
   if (blink::IsRunningPrecompiledCode()) {
     runtime_->dart_controller()->RunFromPrecompiledSnapshot();
   } else {
     std::vector<uint8_t> kernel;
     if (GetAssetAsBuffer(blink::kKernelAssetKey, &kernel)) {
-      runtime_->dart_controller()->RunFromKernel(kernel.data(), kernel.size());
+      runtime_->dart_controller()->RunFromKernel(kernel);
       return;
     }
     std::vector<uint8_t> snapshot;
@@ -425,11 +428,13 @@ void Engine::ConfigureAssetBundle(const std::string& path) {
   }
 }
 
-void Engine::ConfigureRuntime(const std::string& script_uri) {
+void Engine::ConfigureRuntime(const std::string& script_uri,
+    const std::vector<uint8_t>& platform_kernel) {
   runtime_ = blink::RuntimeController::Create(this);
   runtime_->CreateDartController(std::move(script_uri),
                                  default_isolate_snapshot_data,
-                                 default_isolate_snapshot_instr);
+                                 default_isolate_snapshot_instr,
+                                 platform_kernel);
   runtime_->SetViewportMetrics(viewport_metrics_);
   runtime_->SetLocale(language_code_, country_code_);
   runtime_->SetSemanticsEnabled(semantics_enabled_);

engine/src/flutter/shell/common/engine.h

@@ -84,7 +84,8 @@ class Engine : public blink::RuntimeDelegate {
   void StartAnimatorIfPossible();
 
   void ConfigureAssetBundle(const std::string& path);
-  void ConfigureRuntime(const std::string& script_uri);
+  void ConfigureRuntime(const std::string& script_uri,
+      const std::vector<uint8_t>& platform_kernel = std::vector<uint8_t>());
 
   bool HandleLifecyclePlatformMessage(blink::PlatformMessage* message);
   bool HandleNavigationPlatformMessage(