Bug 1370412 - Part 8a. Add "substitutable" flag to ISurfaceProvider state to indicate when the caller won't accept substitutes. r=tnikkel

When SurfaceCache::Lookup is called to access surface data, it indicates
that the caller will not accept substitutes as in the case of
SurfaceCache::LookupBestMatch. As such, we need to be careful not to
remove those surfaces from our cache when pruning (in part 8b). This is
the marker used to track that, at some point, there was a caller which
got this surface that would accept no other (e.g. factor of 2 mode must
make an accept for this particular surface).

image/DecoderFactory.cpp

@@ -145,6 +145,9 @@ DecoderFactory::CreateDecoder(DecoderType aType,
     WrapNotNull(new DecodedSurfaceProvider(aImage,
                                            surfaceKey,
                                            WrapNotNull(decoder)));
+  if (aDecoderFlags & DecoderFlags::CANNOT_SUBSTITUTE) {
+    provider->Availability().SetCannotSubstitute();
+  }
 
   // Attempt to insert the surface provider into the surface cache right away so
   // we won't trigger any more decoders with the same parameters.