Finalize a throttled FileReader in stages.

Source/core/fileapi/FileReader.cpp

Index: Source/core/fileapi/FileReader.cpp
diff --git a/Source/core/fileapi/FileReader.cpp b/Source/core/fileapi/FileReader.cpp
index 012d118b6a57988c1a56fbdc0da7cbf0870b2c48..d1f970158e0cc78b09e2580658f302fd976eefd7 100644
--- a/Source/core/fileapi/FileReader.cpp
+++ b/Source/core/fileapi/FileReader.cpp
@@ -75,12 +75,15 @@ public:
     ThrottlingController() : m_maxRunningReaders(kMaxOutstandingRequestsPerThread) { }
     ~ThrottlingController() { }
 
+    enum FinishReaderType { DoNotRunPendingReaders, RunPendingReaders };
+
     void pushReader(FileReader* reader)
     {
         reader->setPendingActivity(reader);
         if (m_pendingReaders.isEmpty()
             && m_runningReaders.size() < m_maxRunningReaders) {
             reader->executePendingRead();
+            ASSERT(!m_runningReaders.contains(reader));
             m_runningReaders.add(reader);
             return;
         }
@@ -88,23 +91,28 @@ public:
         executeReaders();
     }
 
-    void removeReader(FileReader* reader)
+    FinishReaderType removeReader(FileReader* reader)
     {
         HashSet<FileReader*>::const_iterator hashIter = m_runningReaders.find(reader);
         if (hashIter != m_runningReaders.end()) {
             m_runningReaders.remove(hashIter);
-            reader->unsetPendingActivity(reader);
-            executeReaders();
-            return;
+            return RunPendingReaders;
         }
         Deque<FileReader*>::const_iterator dequeEnd = m_pendingReaders.end();
         for (Deque<FileReader*>::const_iterator it = m_pendingReaders.begin(); it != dequeEnd; ++it) {
             if (*it == reader) {
                 m_pendingReaders.remove(it);
-                reader->unsetPendingActivity(reader);
-                return;
+                break;
             }
         }
+        return DoNotRunPendingReaders;
+    }
+
+    void finishReader(FileReader* reader, FinishReaderType nextStep)
+    {
+        reader->unsetPendingActivity(reader);
+        if (nextStep == RunPendingReaders)
+            executeReaders();
     }
 
 private:
@@ -154,7 +162,7 @@ const AtomicString& FileReader::interfaceName() const
 void FileReader::stop()
 {
     if (m_loadingState == LoadingStateLoading || m_loadingState == LoadingStatePending)
-        throttlingController()->removeReader(this);
+        throttlingController()->finishReader(this, throttlingController()->removeReader(this));
     terminate();
 }
 
@@ -267,12 +275,15 @@ void FileReader::doAbort()
 
     m_error = FileError::create(FileError::ABORT_ERR);
 
+    // Unregister the reader.
+    ThrottlingController::FinishReaderType finalStep = throttlingController()->removeReader(this);
+
     fireEvent(EventTypeNames::error);
     fireEvent(EventTypeNames::abort);
     fireEvent(EventTypeNames::loadend);
 
     // All possible events have fired and we're done, no more pending activity.
-    throttlingController()->removeReader(this);
+    throttlingController()->finishReader(this, finalStep);
 }
 
 void FileReader::terminate()
@@ -318,11 +329,14 @@ void FileReader::didFinishLoading()
     ASSERT(m_state != DONE);
     m_state = DONE;
 
+    // Unregister the reader.
+    ThrottlingController::FinishReaderType finalStep = throttlingController()->removeReader(this);
+
     fireEvent(EventTypeNames::load);
     fireEvent(EventTypeNames::loadend);
 
     // All possible events have fired and we're done, no more pending activity.
-    throttlingController()->removeReader(this);
+    throttlingController()->finishReader(this, finalStep);
 }
 
 void FileReader::didFail(FileError::ErrorCode errorCode)
@@ -336,11 +350,15 @@ void FileReader::didFail(FileError::ErrorCode errorCode)
     m_state = DONE;
 
     m_error = FileError::create(static_cast<FileError::ErrorCode>(errorCode));
+
+    // Unregister the reader.
+    ThrottlingController::FinishReaderType finalStep = throttlingController()->removeReader(this);
+
     fireEvent(EventTypeNames::error);
     fireEvent(EventTypeNames::loadend);
 
     // All possible events have fired and we're done, no more pending activity.
-    throttlingController()->removeReader(this);
+    throttlingController()->finishReader(this, finalStep);
 }
 
 void FileReader::fireEvent(const AtomicString& type)