lowlevel/img.sky flaky crashes

We don't need to pump pending speculations if we don't have any.

R=esprehn@chromium.org, eseidel@chromium.org
BUG=447763

Review URL: https://codereview.chromium.org/852043003

engine/core/html/parser/HTMLDocumentParser.cpp

@@ -388,6 +388,8 @@ void HTMLDocumentParser::resumeAfterWaitingForImports()
         m_scriptRunner.executePendingScripts();
     ASSERT(!isExecutingScript());
     ASSERT(!isWaitingForScripts());
+    if (m_speculations.isEmpty())
+        return;
     ASSERT(m_haveBackgroundParser);
     pumpPendingSpeculations();
 }