Bug 1171356 - On B2G, retry image decodes that fail because allocation of the first frame failed. r=tn

b2g/app/b2g.js

@@ -332,6 +332,7 @@ pref("media.video-queue.default-size", 3);
 pref("image.downscale-during-decode.enabled", true);
 pref("image.decode-only-on-draw.enabled", false);
 pref("image.mem.allow_locking_in_content_processes", true);
+pref("image.decode.retry-on-alloc-failure", true);
 // Limit the surface cache to 1/8 of main memory or 128MB, whichever is smaller.
 // Almost everything that was factored into 'max_decoded_image_kb' is now stored
 // in the surface cache.  1/8 of main memory is 32MB on a 256MB device, which is

gfx/thebes/gfxPrefs.h

@@ -256,6 +256,7 @@ private:
   DECL_GFX_PREF(Once, "image.cache.timeweight",                ImageCacheTimeWeight, int32_t, 500);
   DECL_GFX_PREF(Live, "image.decode-only-on-draw.enabled",     ImageDecodeOnlyOnDrawEnabled, bool, true);
   DECL_GFX_PREF(Live, "image.decode-immediately.enabled",      ImageDecodeImmediatelyEnabled, bool, false);
+  DECL_GFX_PREF(Once, "image.decode.retry-on-alloc-failure",   ImageDecodeRetryOnAllocFailure, bool, false);
   DECL_GFX_PREF(Live, "image.downscale-during-decode.enabled", ImageDownscaleDuringDecodeEnabled, bool, true);
   DECL_GFX_PREF(Live, "image.high_quality_downscaling.enabled", ImageHQDownscalingEnabled, bool, false);
   DECL_GFX_PREF(Live, "image.high_quality_downscaling.min_factor", ImageHQDownscalingMinFactor, uint32_t, 1000);

image/RasterImage.cpp

@@ -262,6 +262,7 @@ RasterImage::RasterImage(ImageURL* aURI /* = nullptr */) :
 #endif
   mSourceBuffer(new SourceBuffer()),
   mFrameCount(0),
+  mRetryCount(0),
   mHasSize(false),
   mDecodeOnlyOnDraw(false),
   mTransient(false),
@@ -1342,6 +1343,31 @@ RasterImage::CanDiscard() {
          !mAnim;                 // Can never discard animated images
 }
 
+class RetryDecodeRunnable : public nsRunnable
+{
+public:
+  RetryDecodeRunnable(RasterImage* aImage,
+                      const IntSize& aSize,
+                      uint32_t aFlags)
+    : mImage(aImage)
+    , mSize(aSize)
+    , mFlags(aFlags)
+  {
+    MOZ_ASSERT(aImage);
+  }
+
+  NS_IMETHOD Run()
+  {
+    mImage->RequestDecodeForSize(mSize, mFlags);
+    return NS_OK;
+  }
+
+private:
+  nsRefPtr<RasterImage> mImage;
+  const IntSize mSize;
+  const uint32_t mFlags;
+};
+
 // Sets up a decoder for this image.
 already_AddRefed<Decoder>
 RasterImage::CreateDecoder(const Maybe<IntSize>& aSize, uint32_t aFlags)
@@ -1418,6 +1444,33 @@ RasterImage::CreateDecoder(const Maybe<IntSize>& aSize, uint32_t aFlags)
                           SurfaceFormat::B8G8R8A8);
     decoder->AllocateFrame(*aSize);
   }
+
+  if (aSize && decoder->HasError()) {
+    if (gfxPrefs::ImageDecodeRetryOnAllocFailure() &&
+        mRetryCount < 10) {
+      // We couldn't allocate the first frame for this image. We're probably in
+      // a temporary low-memory situation, so fire off a runnable and hope that
+      // things have improved when it runs. (Unless we've already retried 10
+      // times in a row, in which case just give up.)
+      mRetryCount++;
+
+      if (decoder->ImageIsLocked()) {
+        UnlockImage();
+      }
+      decoder->TakeProgress();
+      decoder->TakeInvalidRect();
+
+      nsCOMPtr<nsIRunnable> runnable =
+        new RetryDecodeRunnable(this, *aSize, aFlags);
+      NS_DispatchToMainThread(runnable);
+
+      return nullptr;
+    }
+  } else {
+    // We didn't encounter an error when allocating the first frame.
+    mRetryCount = 0;
+  }
+
   decoder->SetIterator(mSourceBuffer->Iterator());
 
   // Set a target size for downscale-during-decode if applicable.

image/RasterImage.h

@@ -400,6 +400,9 @@ private: // data
   // The number of frames this image has.
   uint32_t                   mFrameCount;
 
+  // The number of times we've retried decoding this image.
+  uint8_t                    mRetryCount;
+
   // Boolean flags (clustered together to conserve space):
   bool                       mHasSize:1;       // Has SetSize() been called?
   bool                       mDecodeOnlyOnDraw:1; // Decoding only on draw?