Bug 458440 - Don't create a speculative parser for an empty string. Also, avoid doing work that the scanner will happily do for us. r+sr=jst

parser/htmlparser/src/nsParser.cpp

@@ -206,6 +206,7 @@ public:
       mCurrentlyParsing(0),
       mNumURIs(0),
       mNumConsumed(0),
+      mContext(nsnull),
       mTerminated(PR_FALSE) {
   }
 
@@ -372,8 +373,10 @@ NS_IMPL_THREADSAFE_ISUPPORTS1(nsSpeculativeScriptThread, nsIRunnable)
 NS_IMETHODIMP
 nsSpeculativeScriptThread::Run()
 {
-  nsScannerIterator start;
-  mScanner->CurrentPosition(start);
+  NS_ASSERTION(!NS_IsMainThread(), "Speculative parsing on the main thread?");
+
+  mNumConsumed = 0;
+
   mTokenizer->WillTokenize(PR_FALSE, &mTokenAllocator);
   while (mKeepParsing) {
     PRBool flushTokens = PR_FALSE;
@@ -382,6 +385,8 @@ nsSpeculativeScriptThread::Run()
       break;
     }
 
+    mNumConsumed += mScanner->Mark();
+
     // TODO Don't pop the tokens.
     CToken *token;
     while (mKeepParsing && NS_SUCCEEDED(rv) && (token = mTokenizer->PopToken())) {
@@ -392,11 +397,6 @@ nsSpeculativeScriptThread::Run()
 
   nsAutoLock al(mLock.get());
 
-  nsScannerIterator end;
-  mScanner->CurrentPosition(end);
-
-  mNumConsumed = Distance(start, end);
-
   mCurrentlyParsing = 0;
   PR_NotifyCondVar(mCVar.get());
   return NS_OK;
@@ -446,6 +446,9 @@ nsSpeculativeScriptThread::StartParsing(nsParser *aParser)
     }
     mTokenizer->CopyState(context->mTokenizer);
     context->mScanner->CopyUnusedData(toScan);
+    if (toScan.IsEmpty()) {
+      return NS_OK;
+    }
   } else if (context == mContext) {
     // Don't parse the same part of the document twice.
     nsScannerIterator end;