Re-introduce forward declaration of WebCompositorAnimation

This change reverts necessary changes in patch
http://crrev.com/413983002 which was needed to successfully rename
WebAnimation to WebCompositorAnimation.

This is the patch 4 of 4 and follows on from http://crrev.com/412123002 

BUG=396358

Review URL: https://codereview.chromium.org/421503002

Cr-Commit-Position: refs/heads/master@{#290729}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@290729 0039d316-1c4b-4281-b951-d872f2087c98

cc/blink/web_animation_impl.cc

@@ -11,7 +11,7 @@
 #include "cc/blink/web_float_animation_curve_impl.h"
 #include "cc/blink/web_scroll_offset_animation_curve_impl.h"
 #include "cc/blink/web_transform_animation_curve_impl.h"
-#include "third_party/WebKit/public/platform/WebCompositorAnimation.h"
+#include "third_party/WebKit/public/platform/WebCompositorAnimationCurve.h"
 
 using cc::Animation;
 using cc::AnimationIdProvider;

cc/blink/web_animation_impl.h

@@ -8,12 +8,15 @@
 #include "base/memory/scoped_ptr.h"
 #include "cc/blink/cc_blink_export.h"
 #include "third_party/WebKit/public/platform/WebCompositorAnimation.h"
-#include "third_party/WebKit/public/platform/WebCompositorAnimationCurve.h"
 
 namespace cc {
 class Animation;
 }
 
+namespace blink {
+class WebCompositorAnimationCurve;
+}
+
 namespace cc_blink {
 
 class WebCompositorAnimationImpl : public blink::WebCompositorAnimation {

cc/blink/web_to_cc_animation_delegate_adapter.cc

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 #include "cc/blink/web_to_cc_animation_delegate_adapter.h"
+#include "third_party/WebKit/public/platform/WebCompositorAnimationDelegate.h"
 
 namespace cc_blink {
 

cc/blink/web_to_cc_animation_delegate_adapter.h

@@ -8,7 +8,10 @@
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "cc/animation/animation_delegate.h"
-#include "third_party/WebKit/public/platform/WebCompositorAnimationDelegate.h"
+
+namespace blink {
+class WebCompositorAnimationDelegate;
+}
 
 namespace cc_blink {