Add UMA to estimate deroppable memory usage of encoded data size in Resources

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

Index: third_party/WebKit/Source/core/fetch/ImageResource.cpp
diff --git a/third_party/WebKit/Source/core/fetch/ImageResource.cpp b/third_party/WebKit/Source/core/fetch/ImageResource.cpp
index 929cb375d24e5dcb1ae3a954288a0506d43996ba..97f790370306ad66ca0d81aecdc6d3de301eff23 100644
--- a/third_party/WebKit/Source/core/fetch/ImageResource.cpp
+++ b/third_party/WebKit/Source/core/fetch/ImageResource.cpp
@@ -23,6 +23,7 @@
 
 #include "core/fetch/ImageResource.h"
 
+#include "base/metrics/histogram_macros.h"
 #include "core/fetch/ImageResourceObserver.h"
 #include "core/fetch/MemoryCache.h"
 #include "core/fetch/ResourceClient.h"
@@ -107,7 +108,8 @@ ImageResource::ImageResource(const ResourceRequest& resourceRequest,
       m_image(nullptr),
       m_hasDevicePixelRatioHeaderValue(false),
       m_isSchedulingReload(false),
-      m_isPlaceholder(isPlaceholder) {
+      m_isPlaceholder(isPlaceholder),
+      m_isRefetchableFromDiskCache(true) {
   RESOURCE_LOADING_DVLOG(1) << "new ImageResource(ResourceRequest) " << this;
 }
 
@@ -118,7 +120,8 @@ ImageResource::ImageResource(blink::Image* image,
       m_image(image),
       m_hasDevicePixelRatioHeaderValue(false),
       m_isSchedulingReload(false),
-      m_isPlaceholder(false) {
+      m_isPlaceholder(false),
+      m_isRefetchableFromDiskCache(true) {
   RESOURCE_LOADING_DVLOG(1) << "new ImageResource(Image) " << this;
   setStatus(Cached);
 }
@@ -174,6 +177,9 @@ void ImageResource::didAddClient(ResourceClient* client) {
   if (m_isSchedulingReload || shouldReloadBrokenPlaceholder())
     return;
 
+  if (client->isRefetchableFromDiskCache())
+    m_isRefetchableFromDiskCache = false;
+
   Resource::didAddClient(client);
 }
 
@@ -252,6 +258,10 @@ void ImageResource::destroyDecodedDataIfPossible() {
     return;
   CHECK(!errorOccurred());
   m_image->destroyDecodedData();
+  if (!isPreloaded() && m_isRefetchableFromDiskCache) {
+    UMA_HISTOGRAM_MEMORY_KB("Memory.Renderer.EstimatedDroppableEncodedSize",
+                            encodedSize() / 1024);
+  }
 }
 
 void ImageResource::doResetAnimation() {