Split ImageResourceClient into ResourceClient and ImageResourceObserver [1/2]

We are planning to move ResourceClient to on-heap, but LayoutObject (an
ImageResourceClient subclass) is hard to move to on-heap.

This series of CLs splits ImageResourceClient into
- ResourceClient (notified via Resource, to be moved to Oilpan heap) and
- ImageResourceObserver (notified via ImageObserver, to remain non-heap)
and makes LayoutObject to be ImageResourceObserver but not ResourceClient.

This is the [1/2] CL that
- Splits ImageResourceClient into ResourceClient and ImageResourceObserver,
- Makes LayoutObject and all of its subclasses (except for LayoutImage and its
  subclasses) to be ImageResourceObserver but not ResourceClient.

LayoutImage will be made non-ResourceClient by the [2/2] CL:
https://codereview.chromium.org/1728313003/.

Original CL: https://codereview.chromium.org/1697713002/ by Nate Chapin.

In addition to Nate's original CL (Patch Set 1), this CL:
- Fixes layout test (Patch Set 2).
- Reuses ResourceClientWalker to iterate ImageResourceObserver (Patch Set 3).
- Handles ResourceClient and ImageResourceObserver more similarly (Patch Set 4).
- Renames methods to reflect whether they are for both ResourceClient and
  ImageResourceObserver (Patch Set 6).

BUG=587663

Review URL: https://codereview.chromium.org/1706083002

Cr-Commit-Position: refs/heads/master@{#383425}

1 files changed, 3 insertions, 4 deletions

diff --git a/third_party/WebKit/Source/core/fetch/ImageResourceTest.cpp b/third_party/WebKit/Source/core/fetch/ImageResourceTest.cpp
index c3ecd53..4e7a570 100644
--- a/third_party/WebKit/Source/core/fetch/ImageResourceTest.cpp
+++ b/third_party/WebKit/Source/core/fetch/ImageResourceTest.cpp
@@ -30,9 +30,8 @@
 
 #include "core/fetch/ImageResource.h"
 
-#include "core/fetch/ImageResourceClient.h"
 #include "core/fetch/MemoryCache.h"
-#include "core/fetch/MockImageResourceClient.h"
+#include "core/fetch/MockResourceClients.h"
 #include "core/fetch/ResourceFetcher.h"
 #include "core/fetch/ResourceLoader.h"
 #include "core/fetch/UniqueIdentifier.h"
@@ -195,14 +194,14 @@ TEST(ImageResourceTest, DecodedDataRemainsWhileHasClients)
 
     // The prune comes when the ImageResource still has clients. The image should not be deleted.
     cachedImage->prune();
-    ASSERT_TRUE(cachedImage->hasClients());
+    ASSERT_TRUE(cachedImage->hasClientsOrObservers());
     ASSERT_TRUE(cachedImage->hasImage());
     ASSERT_FALSE(cachedImage->getImage()->isNull());
 
     // The ImageResource no longer has clients. The image should be deleted by prune.
     client.removeAsClient();
     cachedImage->prune();
-    ASSERT_FALSE(cachedImage->hasClients());
+    ASSERT_FALSE(cachedImage->hasClientsOrObservers());
     ASSERT_FALSE(cachedImage->hasImage());
     ASSERT_TRUE(cachedImage->getImage()->isNull());
 }