#501: add toggle pref

gfx/thebes/gfxPrefs.h

@@ -295,6 +295,7 @@ private:
   DECL_GFX_PREF(Live, "image.mozsamplesize.enabled",           ImageMozSampleSizeEnabled, bool, false);
   DECL_GFX_PREF(Once, "image.multithreaded_decoding.limit",    ImageMTDecodingLimit, int32_t, -1);
   DECL_GFX_PREF(Live, "image.single-color-optimization.enabled", ImageSingleColorOptimizationEnabled, bool, true);
+  DECL_GFX_PREF(Live, "image.webp.enabled",                    ImageWebPEnabled, bool, false);
 
   DECL_GFX_PREF(Once, "layers.acceleration.disabled",          LayersAccelerationDisabled, bool, false);
   DECL_GFX_PREF(Live, "layers.acceleration.draw-fps",          LayersDrawFPS, bool, false);

image/DecoderFactory.cpp

@@ -65,7 +65,8 @@ DecoderFactory::GetDecoderType(const char* aMimeType)
     type = DecoderType::ICON;
 
   // WEBP
-  } else if (!strcmp(aMimeType, IMAGE_WEBP)) {
+  } else if (!strcmp(aMimeType, IMAGE_WEBP) &&
+             MOZ_LIKELY(gfxPrefs::ImageWebPEnabled())) {
     type = DecoderType::WEBP;
   }
 
@@ -161,7 +162,8 @@ DecoderFactory::CreateAnimationDecoder(DecoderType aType,
     return nullptr;
   }
 
-  MOZ_ASSERT(aType == DecoderType::GIF || aType == DecoderType::PNG,
+  MOZ_ASSERT(aType == DecoderType::GIF || aType == DecoderType::PNG ||
+             aType == DecoderType::WEBP,
              "Calling CreateAnimationDecoder for non-animating DecoderType");
 
   RefPtr<Decoder> decoder =

modules/libpref/init/all.js

@@ -4193,6 +4193,9 @@ pref("image.mem.surfacecache.discard_factor", 1);
 // automatically determined based on the system's number of cores.
 pref("image.multithreaded_decoding.limit", -1);
 
+// Whether we attempt to decode WebP images or not.
+pref("image.webp.enabled", true);
+
 // Limit for the canvas image cache. 0 means we don't limit the size of the
 // cache.
 pref("canvas.image.cache.limit", 0);