Explicitly clear the image in the first updateImage() call

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

Index: third_party/WebKit/Source/core/loader/resource/ImageResource.h
diff --git a/third_party/WebKit/Source/core/loader/resource/ImageResource.h b/third_party/WebKit/Source/core/loader/resource/ImageResource.h
index 3872761ac4bf6f0448d118f47e8bff1a1a5c7a16..eecb2c080c139bd28ade22a7243cbe3f56d89a07 100644
--- a/third_party/WebKit/Source/core/loader/resource/ImageResource.h
+++ b/third_party/WebKit/Source/core/loader/resource/ImageResource.h
@@ -25,6 +25,7 @@
 
 #include "core/CoreExport.h"
 #include "core/fetch/Resource.h"
+#include "core/loader/resource/ImageResourceContent.h"
 #include "core/loader/resource/ImageResourceInfo.h"
 #include "core/loader/resource/MultipartImageResourceParser.h"
 #include "platform/Timer.h"
@@ -129,6 +130,12 @@ class CORE_EXPORT ImageResource final
   void destroyDecodedDataIfPossible() override;
   void destroyDecodedDataForFailedRevalidation() override;
 
+  // When UpdateImageOption is UpdateImage but this is the first
+  // updateImage() call, then ClearAndUpdateImage is used instead to enforce
+  // new image creation.
+  void updateImage(PassRefPtr<SharedBuffer>,
+                   ImageResourceContent::UpdateImageOption,
+                   bool allDataReceived);
   void flushImageIfNeeded(TimerBase*);
 
   bool shouldReloadBrokenPlaceholder() const {
@@ -139,6 +146,11 @@ class CORE_EXPORT ImageResource final
 
   Member<ImageResourceContent> m_content;
 
+  // Indicates whether updateImage() is called for this resource, or for this
+  // part (in case of multipart images), and is used for enforcing creation of
+  // new blink::Image in ImageResourceContent for the first updateImage().
+  bool m_isUpdateImageCalled = false;

[kouhei (in TOK), 2016/12/19 01:32:04]

This flag name is quite confusing, as onePartIn~() also updates this.
Would inverting this flag & renaming this to "m_shouldEnforceClearImage" make
sense?

Would you document somewhere why we have this
ImageResourceContent::ClearImageOption in the first place?

[hiroshige, 2016/12/27 23:25:31]

Done in Patch Set 10.
Done (in https://codereview.chromium.org/2587503002/ Patch Set 6).

+
   // TODO(hiroshige): move |m_devicePixelRatioHeaderValue| and
   // |m_hasDevicePixelRatioHeaderValue| to ImageResourceContent and update
   // it via ImageResourceContent::updateImage().