Bug 1333990: Part 2a - Allow multiple concurrent parser blockers. r=hsivonen

MozReview-Commit-ID: DYegic0RPWL

--HG--
extra : rebase_source : 959fae62e924ee9f27f00378a26f752bb0307bb1

parser/html/nsHtml5Parser.cpp

@@ -37,7 +37,7 @@ NS_IMPL_CYCLE_COLLECTION_UNLINK_END
 nsHtml5Parser::nsHtml5Parser()
   : mLastWasCR(false)
   , mDocWriteSpeculativeLastWasCR(false)
-  , mBlocked(false)
+  , mBlocked(0)
   , mDocWriteSpeculatorActive(false)
   , mInsertionPointPushLevel(0)
   , mDocumentClosed(false)
@@ -146,14 +146,19 @@ nsHtml5Parser::ContinueInterruptedParsing()
 NS_IMETHODIMP_(void)
 nsHtml5Parser::BlockParser()
 {
-  mBlocked = true;
+  mBlocked++;
 }
 
 NS_IMETHODIMP_(void)
 nsHtml5Parser::UnblockParser()
 {
-  mBlocked = false;
-  mExecutor->ContinueInterruptedParsingAsync();
+  MOZ_DIAGNOSTIC_ASSERT(mBlocked > 0);
+  if (MOZ_LIKELY(mBlocked > 0)) {
+    mBlocked--;
+  }
+  if (MOZ_LIKELY(mBlocked == 0)) {
+    mExecutor->ContinueInterruptedParsingAsync();
+  }
 }
 
 NS_IMETHODIMP_(void)

parser/html/nsHtml5Parser.h

@@ -278,9 +278,10 @@ class nsHtml5Parser final : public nsIParser,
     bool                          mDocWriteSpeculativeLastWasCR;
 
     /**
-     * The parser is blocking on a script
+     * The parser is blocking on the load of an external script from a web
+     * page, or any number of extension content scripts.
      */
-    bool                          mBlocked;
+    uint32_t                      mBlocked;
 
     /**
      * Whether the document.write() speculator is already active.

parser/htmlparser/nsParser.cpp

@@ -45,7 +45,6 @@
 using namespace mozilla;
 using mozilla::dom::EncodingUtils;
 
-#define NS_PARSER_FLAG_PARSER_ENABLED         0x00000002
 #define NS_PARSER_FLAG_OBSERVERS_ENABLED      0x00000004
 #define NS_PARSER_FLAG_PENDING_CONTINUE_EVENT 0x00000008
 #define NS_PARSER_FLAG_FLUSH_TOKENS           0x00000020
@@ -157,8 +156,8 @@ nsParser::Initialize(bool aConstructor)
   mInternalState = NS_OK;
   mStreamStatus = NS_OK;
   mCommand = eViewNormal;
+  mBlocked = 0;
   mFlags = NS_PARSER_FLAG_OBSERVERS_ENABLED |
-           NS_PARSER_FLAG_PARSER_ENABLED |
            NS_PARSER_FLAG_CAN_TOKENIZE;
 
   mProcessingNetworkData = false;
@@ -631,7 +630,7 @@ nsParser::ContinueInterruptedParsing()
   nsCOMPtr<nsIContentSink> sinkDeathGrip(mSink);
 
 #ifdef DEBUG
-  if (!(mFlags & NS_PARSER_FLAG_PARSER_ENABLED)) {
+  if (mBlocked) {
     NS_WARNING("Don't call ContinueInterruptedParsing on a blocked parser.");
   }
 #endif
@@ -654,13 +653,15 @@ nsParser::ContinueInterruptedParsing()
 }
 
 /**
- *  Stops parsing temporarily. That's it will prevent the
- *  parser from building up content model.
+ *  Stops parsing temporarily. That is, it will prevent the
+ *  parser from building up content model while scripts
+ *  are being loaded (either an external script from a web
+ *  page, or any number of extension content scripts).
  */
 NS_IMETHODIMP_(void)
 nsParser::BlockParser()
 {
-  mFlags &= ~NS_PARSER_FLAG_PARSER_ENABLED;
+  mBlocked++;
 }
 
 /**
@@ -672,10 +673,9 @@ nsParser::BlockParser()
 NS_IMETHODIMP_(void)
 nsParser::UnblockParser()
 {
-  if (!(mFlags & NS_PARSER_FLAG_PARSER_ENABLED)) {
-    mFlags |= NS_PARSER_FLAG_PARSER_ENABLED;
-  } else {
-    NS_WARNING("Trying to unblock an unblocked parser.");
+  MOZ_DIAGNOSTIC_ASSERT(mBlocked > 0);
+  if (MOZ_LIKELY(mBlocked > 0)) {
+    mBlocked--;
   }
 }
 
@@ -691,7 +691,7 @@ nsParser::ContinueInterruptedParsingAsync()
 NS_IMETHODIMP_(bool)
 nsParser::IsParserEnabled()
 {
-  return (mFlags & NS_PARSER_FLAG_PARSER_ENABLED) != 0;
+  return !mBlocked;
 }
 
 /**
@@ -1024,8 +1024,7 @@ nsParser::ResumeParse(bool allowIteration, bool aIsFinalChunk,
 {
   nsresult result = NS_OK;
 
-  if ((mFlags & NS_PARSER_FLAG_PARSER_ENABLED) &&
-      mInternalState != NS_ERROR_HTMLPARSER_STOPPARSING) {
+  if (!mBlocked && mInternalState != NS_ERROR_HTMLPARSER_STOPPARSING) {
 
     result = WillBuildModel(mParserContext->mScanner->GetFilename());
     if (NS_FAILED(result)) {
@@ -1070,7 +1069,7 @@ nsParser::ResumeParse(bool allowIteration, bool aIsFinalChunk,
         // (and cache any data coming in) until the parser is re-enabled.
         if (NS_ERROR_HTMLPARSER_BLOCK == result) {
           mSink->WillInterrupt();
-          if (mFlags & NS_PARSER_FLAG_PARSER_ENABLED) {
+          if (!mBlocked) {
             // If we were blocked by a recursive invocation, don't re-block.
             BlockParser();
           }

parser/htmlparser/nsParser.h

@@ -385,6 +385,7 @@ protected:
     int32_t             mCharsetSource;
     
     uint16_t            mFlags;
+    uint32_t            mBlocked;
 
     nsString            mUnusedInput;
     nsCString           mCharset;