Adds a CancellableTaskFactory and exposes postLoadingTasks to Blink

Source/core/html/parser/HTMLDocumentParser.cpp

Index: Source/core/html/parser/HTMLDocumentParser.cpp
diff --git a/Source/core/html/parser/HTMLDocumentParser.cpp b/Source/core/html/parser/HTMLDocumentParser.cpp
index 494e626632747c47732fd85919edf1c039b0c49f..42afc34feadad9a77fce0a28becff2709a8bc364 100644
--- a/Source/core/html/parser/HTMLDocumentParser.cpp
+++ b/Source/core/html/parser/HTMLDocumentParser.cpp
@@ -530,6 +530,10 @@ void HTMLDocumentParser::pumpPendingSpeculations()
     SpeculationsPumpSession session(m_pumpSpeculationsSessionNestingLevel, contextForParsingSession());
     while (!m_speculations.isEmpty()) {
         ASSERT(!isScheduledForResume());
+
+        if (m_parserScheduler->yieldIfNeeded(session, m_speculations.first()->startingScript))

[Sami, 2015/01/26 18:07:41]

I wonder if we should move this yield point in a separate patch? I foresee much
flake in our future :)

[alex clarke (OOO till 29th), 2015/01/27 11:41:19]

Done.

+            break;
+
         size_t elementTokenCount = processParsedChunkFromBackgroundParser(m_speculations.takeFirst());
         session.addedElementTokens(elementTokenCount);
 
@@ -539,9 +543,6 @@ void HTMLDocumentParser::pumpPendingSpeculations()
         // which invokes nested event loops. (e.g. inspector breakpoints)
         if (!isParsing() || isWaitingForScripts() || isScheduledForResume())
             break;
-
-        if (m_speculations.isEmpty() || m_parserScheduler->yieldIfNeeded(session, m_speculations.first()->startingScript))
-            break;
     }
 
     TRACE_EVENT_END1(TRACE_DISABLED_BY_DEFAULT("devtools.timeline"), "ParseHTML", "endLine", lineNumber().zeroBasedInt());