cros: Add UMA stat for graphics driver memory on tab discard

chrome/browser/memory_details.cc

Index: chrome/browser/memory_details.cc
diff --git a/chrome/browser/memory_details.cc b/chrome/browser/memory_details.cc
index 0d391d994098bd76558cbb04a83a273cf673c6a0..facdae9ad5cce281601e1e9415e3875c029e4a8f 100644
--- a/chrome/browser/memory_details.cc
+++ b/chrome/browser/memory_details.cc
@@ -459,6 +459,13 @@ void MemoryDetails::UpdateHistograms() {
   }
   UMA_HISTOGRAM_MEMORY_KB("Memory.BackingStore",
                           RenderWidgetHost::BackingStoreMemorySize() / 1024);
+#if defined(OS_CHROMEOS)
+  // Chrome OS exposes system-wide graphics driver memory which has historically
+  // been a source of leak/bloat.
+  base::SystemMemoryInfoKB meminfo;
+  if (base::GetSystemMemoryInfo(&meminfo) && meminfo.gem_size != -1)
+    UMA_HISTOGRAM_MEMORY_MB("Memory.Graphics", meminfo.gem_size / 1024 / 1024);
+#endif
 
   UMA_HISTOGRAM_COUNTS_100("Memory.ProcessCount",
       static_cast<int>(browser.processes.size()));