[tracing] Support BACKGROUND mode in MemoryCache dump provider

third_party/WebKit/Source/core/fetch/ImageResource.h

Index: third_party/WebKit/Source/core/fetch/ImageResource.h
diff --git a/third_party/WebKit/Source/core/fetch/ImageResource.h b/third_party/WebKit/Source/core/fetch/ImageResource.h
index b0038b3e5f0139b08fdd8114700db9ffec88308d..802bc3b10d7062495556711bcf024ce7180eed05 100644
--- a/third_party/WebKit/Source/core/fetch/ImageResource.h
+++ b/third_party/WebKit/Source/core/fetch/ImageResource.h
@@ -110,6 +110,8 @@ public:
     void responseReceived(const ResourceResponse&, std::unique_ptr<WebDataConsumerHandle>) override;
     void finish(double finishTime = 0.0) override;
 
+    void onMemoryDump(WebMemoryDumpLevelOfDetail, WebProcessMemoryDump*) const override;
+
     // For compatibility, images keep loading even if there are HTTP errors.
     bool shouldIgnoreHTTPStatusCodeErrors() const override { return true; }