Properly suspend HTMLDocumentParser

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 6550314ea84dcfcda1d5c7d343b5027dd2216d9a..e599417a30d3716d66c28d0b6c69d8c0283aece9 100644
--- a/Source/core/html/parser/HTMLDocumentParser.cpp
+++ b/Source/core/html/parser/HTMLDocumentParser.cpp
@@ -116,6 +116,7 @@ HTMLDocumentParser::HTMLDocumentParser(HTMLDocument& document, bool reportErrors
     , m_isPinnedToMainThread(false)
     , m_endWasDelayed(false)
     , m_haveBackgroundParser(false)
+    , m_tasksWereSuspended(false)
     , m_pumpSessionNestingLevel(0)
 {
     ASSERT(shouldUseThreading() || (m_token && m_tokenizer));
@@ -134,6 +135,7 @@ HTMLDocumentParser::HTMLDocumentParser(DocumentFragment* fragment, Element* cont
     , m_isPinnedToMainThread(true)
     , m_endWasDelayed(false)
     , m_haveBackgroundParser(false)
+    , m_tasksWereSuspended(false)
     , m_pumpSessionNestingLevel(0)
 {
     ASSERT(!shouldUseThreading());
@@ -281,14 +283,15 @@ void HTMLDocumentParser::resumeParsingAfterYield()
     // but we need to ensure it isn't deleted yet.
     RefPtrWillBeRawPtr<HTMLDocumentParser> protect(this);
 
-    if (m_haveBackgroundParser) {
+    if (m_haveBackgroundParser || !m_speculations.isEmpty()) {

[João Eiras, 2014/10/06 12:14:30]

I'm a bit unsure about how these two variables relate, hence I modified this
check because m_speculations is being added the chunks when the parser is
suspended. If you tell me that m_speculations depend on m_haveBackgroundParser
being set to true, then I can revert this line.

[eseidel, 2014/10/06 18:07:08]

Speculations are parsed chunks sent to us from the background parser.  Unclear
how you could ever have speculations and not have a background parser...

[João Eiras, 2014/10/07 13:25:07]

OK, line reverted.

         pumpPendingSpeculations();
         return;
     }
 
     // We should never be here unless we can pump immediately.  Call pumpTokenizer()
     // directly so that ASSERTS will fire if we're wrong.
-    pumpTokenizer(AllowYield);
+    if (m_tokenizer)

[João Eiras, 2014/10/06 12:14:31]

As consequence of forcing a call to this method when resumeScheduledTasks is
called, m_tokenizer will be empty for document that have done all their parsing.
Instead of adding even more state to know if
didReceiveParsedChunkFromBackgroundParser was called or not, this is the
simplest way I found to avoid the assert inside pumpTokenizer().

[eseidel, 2014/10/06 18:07:08]

This seems wrong.  We should just be more careful as to when we call this
method.

[João Eiras, 2014/10/07 13:25:07]

Ok, added a couple extra checks in HTMLDocumentParser::resumeScheduledTasks()
then

+        pumpTokenizer(AllowYield);
     endIfDelayed();
 }
 
@@ -349,7 +352,7 @@ void HTMLDocumentParser::didReceiveParsedChunkFromBackgroundParser(PassOwnPtr<Pa
     // alert(), runModalDialog, and the JavaScript Debugger all run nested event loops
     // which can cause this method to be re-entered. We detect re-entry using
     // hasActiveParser(), save the chunk as a speculation, and return.
-    if (isWaitingForScripts() || !m_speculations.isEmpty() || document()->activeParserCount() > 0) {
+    if (isWaitingForScripts() || !m_speculations.isEmpty() || document()->activeParserCount() > 0 || m_tasksWereSuspended) {
         m_preloader->takeAndPreload(chunk->preloads);
         m_speculations.append(chunk);
         return;
@@ -1029,14 +1032,18 @@ void HTMLDocumentParser::parseDocumentFragment(const String& source, DocumentFra
 
 void HTMLDocumentParser::suspendScheduledTasks()
 {
+    ASSERT(!m_tasksWereSuspended);
+    m_tasksWereSuspended = true;
     if (m_parserScheduler)
         m_parserScheduler->suspend();
 }
 
 void HTMLDocumentParser::resumeScheduledTasks()
 {
+    ASSERT(m_tasksWereSuspended);
+    m_tasksWereSuspended = false;
     if (m_parserScheduler)
-        m_parserScheduler->resume();
+        m_parserScheduler->scheduleForResume();
 }
 
 void HTMLDocumentParser::appendBytes(const char* data, size_t length)