Plugin Power Saver: Add some UMAs to test plugins in wild.

content/renderer/pepper/plugin_power_saver_helper.cc

Index: content/renderer/pepper/plugin_power_saver_helper.cc
diff --git a/content/renderer/pepper/plugin_power_saver_helper.cc b/content/renderer/pepper/plugin_power_saver_helper.cc
index 13c079ee1c876503c7f49eeb5416aaa4958b3265..7d434ecd395173e6348b6c3609fe692e0d973373 100644
--- a/content/renderer/pepper/plugin_power_saver_helper.cc
+++ b/content/renderer/pepper/plugin_power_saver_helper.cc
@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 #include "base/callback.h"
+#include "base/metrics/histogram.h"
 #include "content/common/frame_messages.h"
 #include "content/public/renderer/document_state.h"
 #include "content/public/renderer/navigation_state.h"
@@ -16,6 +17,19 @@ namespace content {
 
 namespace {
 
+// Initial decision of the peripheral content decision.
+// These numeric values are used in UMA logs; do not change them.
+enum PeripheralHeuristicDecision {
+  PERIPHERAL_HEURISTIC_DECISION_PERIPHERAL = 0,
+  PERIPHERAL_HEURISTIC_DECISION_ESSENTIAL_SAME_ORIGIN = 1,
+  PERIPHERAL_HEURISTIC_DECISION_ESSENTIAL_CROSS_ORIGIN_BIG = 2,
+  PERIPHERAL_HEURISTIC_DECISION_ESSENTIAL_CROSS_ORIGIN_WHITELISTED = 3,
+  PERIPHERAL_HEURISTIC_DECISION_NUM_ITEMS
+};
+
+const char kPeripheralHeuristicHistogram[] =
+    "Plugin.PowerSaverPeripheralHeuristic";
+
 // Maximum dimensions plug-in content may have while still being considered
 // peripheral content. These match the sizes used by Safari.
 const int kPeripheralContentMaxWidth = 400;
@@ -89,24 +103,47 @@ bool PluginPowerSaverHelper::ShouldThrottleContent(const GURL& content_origin,
   // --site-per-process mode.
   blink::WebFrame* main_frame =
       render_frame()->GetWebFrame()->view()->mainFrame();
-  if (main_frame->isWebRemoteFrame())
+  if (main_frame->isWebRemoteFrame()) {
+    UMA_HISTOGRAM_ENUMERATION(kPeripheralHeuristicHistogram,
+                              PERIPHERAL_HEURISTIC_DECISION_PERIPHERAL,
+                              PERIPHERAL_HEURISTIC_DECISION_NUM_ITEMS);

[Ilya Sherman, 2014/11/05 22:36:19]

Optional nit: It's typically useful to define a wrapper function for each
UMA_HISTOGRAM_ENUMERATION, so that you can call
RecordPeripheralHeuristicMetric(PERIPHERAL_HEURISTIC_DECISION_PERIPHERAL).  It
leads to shorter, and thus often more bug-free, code.

[tommycli, 2014/11/06 00:36:05]

Done.

Good suggestion. Can I modify the enum values to be shorter too? Like
DECISION_PERIPHERAL, DECISION_ESSENTIAL_CROSS_ORIGIN_WHITELISTED ?

[Ilya Sherman, 2014/11/06 03:30:30]

My understanding of the style guide is that you can use a class enum, and then
have shorter constant names.  Honestly, for an enum that's defined in the
anonymous namespace, and hence not visible externally to this compilation unit,
you can probably use short constant names anyway.  But, that's more a matter for
this file's OWNERS to weigh in on, if they care to.

[tommycli, 2014/11/06 21:16:13]

Done.

     return true;
+  }
 
   // All same-origin plugin content is essential.
   GURL main_frame_origin = GURL(main_frame->document().url()).GetOrigin();
   if (content_origin == main_frame_origin) {
+    UMA_HISTOGRAM_ENUMERATION(
+        kPeripheralHeuristicHistogram,
+        PERIPHERAL_HEURISTIC_DECISION_ESSENTIAL_SAME_ORIGIN,
+        PERIPHERAL_HEURISTIC_DECISION_NUM_ITEMS);
     *cross_origin = false;
     return false;
   }
 
   // Whitelisted plugin origins are also essential.
-  if (origin_whitelist_.count(content_origin))
+  if (origin_whitelist_.count(content_origin)) {
+    UMA_HISTOGRAM_ENUMERATION(
+        kPeripheralHeuristicHistogram,
+        PERIPHERAL_HEURISTIC_DECISION_ESSENTIAL_CROSS_ORIGIN_WHITELISTED,
+        PERIPHERAL_HEURISTIC_DECISION_NUM_ITEMS);
     return false;
+  }
 
   // Cross-origin plugin content is peripheral if smaller than a maximum size.
   bool content_is_small = width < kPeripheralContentMaxWidth ||
                           height < kPeripheralContentMaxHeight;
 
+  if (content_is_small) {
+    UMA_HISTOGRAM_ENUMERATION(kPeripheralHeuristicHistogram,
+                              PERIPHERAL_HEURISTIC_DECISION_PERIPHERAL,
+                              PERIPHERAL_HEURISTIC_DECISION_NUM_ITEMS);
+  } else {
+    UMA_HISTOGRAM_ENUMERATION(
+        kPeripheralHeuristicHistogram,
+        PERIPHERAL_HEURISTIC_DECISION_ESSENTIAL_CROSS_ORIGIN_BIG,
+        PERIPHERAL_HEURISTIC_DECISION_NUM_ITEMS);
+  }
   return content_is_small;
 }