Phase III Step 2: Call imageNotifyFinished() and image load event after SVG loading completes

third_party/WebKit/Source/core/loader/resource/ImageResource.cpp

Index: third_party/WebKit/Source/core/loader/resource/ImageResource.cpp
diff --git a/third_party/WebKit/Source/core/loader/resource/ImageResource.cpp b/third_party/WebKit/Source/core/loader/resource/ImageResource.cpp
index 685fac75d9a2f8d9c0a4e5aff7e00f239d1df7b4..c9026fb379521115c2dc1c64c31b3679e73406cd 100644
--- a/third_party/WebKit/Source/core/loader/resource/ImageResource.cpp
+++ b/third_party/WebKit/Source/core/loader/resource/ImageResource.cpp
@@ -181,6 +181,16 @@ bool ImageResource::CanReuse(const FetchParameters& params) const {
   return true;
 }
 
+bool ImageResource::CanUseCacheValidator() const {
+  // Disable revalidation while ImageResourceContent is still waiting for
+  // SVG load completion.
+  // TODO(hiroshige): Clean up revalidation-related dependencies.
+  if (!GetContent()->IsLoaded())

[hiroshige, 2017/05/04 22:50:50]

This is not clean, but ImageResourceContent has already special logics for
revalidation (e.g. IsCacheValidator() call in AddObserver()).

However, I expect allowing revalidation during waiting for SVG load complicates
the state transition much more.
Consider the following scenario:
(1) DidFinishLoading() for an SVG image is called, and we start waiting SVG load
completion. GetContentState() is kPending.
(2) Revalidation starts.
(3) SVG load completes.
    At this time, I think we shouldn't notify observers nor change the state to
kCached, because we are in the middle of revalidation.
(4) Revalidation response is received and its 304.
    The original SVG image continues to be used, and thus we have to notify its
load completion. Therefore, we have to remember the notification at Step (3) and
then process it here in Step (4).

+    return false;
+
+  return Resource::CanUseCacheValidator();
+}
+
 ImageResource* ImageResource::Create(const ResourceRequest& request) {
   return new ImageResource(request, ResourceLoaderOptions(),
                            ImageResourceContent::Create(), false);