content: Remove blimp compositing dependencies.

content/test/fake_compositor_dependencies.cc

Index: content/test/fake_compositor_dependencies.cc
diff --git a/content/test/fake_compositor_dependencies.cc b/content/test/fake_compositor_dependencies.cc
index a59e615a14d3663101e84f6ad368640cec90da40..d457c99b67bbf5e00488b0173866e841a893ce01 100644
--- a/content/test/fake_compositor_dependencies.cc
+++ b/content/test/fake_compositor_dependencies.cc
@@ -80,11 +80,6 @@ FakeCompositorDependencies::GetRendererScheduler() {
   return &renderer_scheduler_;
 }
 
-cc::ImageSerializationProcessor*
-FakeCompositorDependencies::GetImageSerializationProcessor() {
-  return nullptr;
-}
-
 cc::TaskGraphRunner* FakeCompositorDependencies::GetTaskGraphRunner() {
   return &task_graph_runner_;
 }