Replace image_messages.h with Mojo service

content/test/test_web_contents.h

Index: content/test/test_web_contents.h
diff --git a/content/test/test_web_contents.h b/content/test/test_web_contents.h
index 798a54d9540a8d58f99ad5746601def9abd7cbee..fd3a3be4656923a41e94010349f0aa91be1e3cf6 100644
--- a/content/test/test_web_contents.h
+++ b/content/test/test_web_contents.h
@@ -35,6 +35,12 @@ class TestWebContents : public WebContentsImpl, public WebContentsTester {
   // WebContentsImpl overrides (returning the same values, but in Test* types)
   TestRenderFrameHost* GetMainFrame() override;
   TestRenderViewHost* GetRenderViewHost() const override;
+  // Overrides to avoid establishing Mojo connection with renderer process.
+  int DownloadImage(const GURL& url,
+                    bool is_favicon,
+                    uint32_t max_bitmap_size,
+                    bool bypass_cache,
+                    const ImageDownloadCallback& callback) override;
 
   // WebContentsTester implementation.
   void CommitPendingNavigation() override;