Bug 802390 - Gracefully handle shutting down a decoder that hasn't had a chance to do any work. r=jrmuizel

image/src/Decoder.cpp

@@ -80,7 +80,7 @@ Decoder::Write(const char* aBuffer, uint32_t aCount)
 }
 
 void
-Decoder::Finish()
+Decoder::Finish(RasterImage::eShutdownIntent aShutdownIntent)
 {
   // Implementation-specific finalization
   if (!HasError())
@@ -114,16 +114,22 @@ Decoder::Finish()
       }
     }
 
-    // If we only have a data error, see if things are worth salvaging
-    bool salvage = !HasDecoderError() && mImage.GetNumFrames();
+    bool usable = true;
+    if (aShutdownIntent != RasterImage::eShutdownIntent_Interrupted && !HasDecoderError()) {
+      // If we only have a data error, we're usable if we have at least one frame.
+      if (mImage.GetNumFrames() == 0) {
+        usable = false;
+      }
+    }
 
-    // If we're salvaging, say we finished decoding
-    if (salvage)
-      mImage.DecodingComplete();
-
-    // Fire teardown notifications
-    if (mObserver) {
-      mObserver->OnStopDecode(salvage ? NS_OK : NS_ERROR_FAILURE);
+    // If we're usable, do exactly what we should have when the decoder
+    // completed.
+    if (usable) {
+      PostDecodeDone();
+    } else {
+      if (mObserver) {
+        mObserver->OnStopDecode(NS_ERROR_FAILURE);
+      }
     }
   }
 }

image/src/Decoder.h

@@ -59,7 +59,7 @@ public:
    *
    * Notifications Sent: TODO
    */
-  void Finish();
+  void Finish(RasterImage::eShutdownIntent aShutdownIntent);
 
   /**
    * Informs the shared decoder that all the data has been written.

image/src/RasterImage.cpp

@@ -2591,7 +2591,7 @@ RasterImage::ShutdownDecoder(eShutdownIntent aIntent)
 
   mFinishing = true;
   mInDecoder = true;
-  decoder->Finish();
+  decoder->Finish(aIntent);
   mInDecoder = false;
   mFinishing = false;
 

image/src/RasterImage.h

@@ -311,6 +311,14 @@ public:
   // SCALE_INVALID otherwise.
   void ScalingDone(ScaleRequest* request, ScaleStatus status);
 
+  // Decoder shutdown
+  enum eShutdownIntent {
+    eShutdownIntent_Done        = 0,
+    eShutdownIntent_Interrupted = 1,
+    eShutdownIntent_Error       = 2,
+    eShutdownIntent_AllCount    = 3
+  };
+
 private:
   struct Anim
   {
@@ -710,13 +718,6 @@ private: // data
   // will inform us when to let go of this pointer.
   ScaleRequest* mScaleRequest;
 
-  // Decoder shutdown
-  enum eShutdownIntent {
-    eShutdownIntent_Done        = 0,
-    eShutdownIntent_Interrupted = 1,
-    eShutdownIntent_Error       = 2,
-    eShutdownIntent_AllCount    = 3
-  };
   nsresult ShutdownDecoder(eShutdownIntent aIntent);
 
   // Helpers