Add UMA histogram to determine how often Stage3D could be used.

webkit/plugins/ppapi/ppapi_plugin_instance.cc

Index: webkit/plugins/ppapi/ppapi_plugin_instance.cc
diff --git a/webkit/plugins/ppapi/ppapi_plugin_instance.cc b/webkit/plugins/ppapi/ppapi_plugin_instance.cc
index 36569266fbcc26a230ea6c32eafaa6ab587505c1..e81c614977bea07d7bc0ab192d107d34d8c682e9 100644
--- a/webkit/plugins/ppapi/ppapi_plugin_instance.cc
+++ b/webkit/plugins/ppapi/ppapi_plugin_instance.cc
@@ -29,6 +29,7 @@
 #include "ppapi/c/ppp_mouse_lock.h"
 #include "ppapi/c/private/pp_content_decryptor.h"
 #include "ppapi/c/private/ppp_instance_private.h"
+#include "ppapi/shared_impl/ppapi_preferences.h"
 #include "ppapi/shared_impl/ppb_input_event_shared.h"
 #include "ppapi/shared_impl/ppb_url_util_shared.h"
 #include "ppapi/shared_impl/ppb_view_shared.h"
@@ -96,6 +97,7 @@
 
 #if defined(OS_WIN)
 #include "base/metrics/histogram.h"
+#include "base/win/windows_version.h"
 #include "skia/ext/platform_canvas.h"
 #include "ui/gfx/codec/jpeg_codec.h"
 #include "ui/gfx/gdi_util.h"
@@ -544,6 +546,23 @@ bool PluginInstance::Initialize(WebPluginContainer* container,
 
   container_->setIsAcceptingTouchEvents(IsAcceptingTouchEvents());
 
+#if defined(OS_WIN)

[brettw, 2012/08/27 22:19:28]

Can you split this into a separate function?

+  if (base::win::GetVersion() <= base::win::VERSION_XP) {
+    ::ppapi::Preferences prefs = delegate_->GetPreferences();
+    bool needsgpu = false;

[vangelis, 2012/08/28 05:12:06]

nit: according to chrome's variable naming convention this should be needs_gpu

+
+    for (unsigned int i = 0; i < arg_names.size(); i++) {

[brettw, 2012/08/27 22:19:28]

Use size_t since that's the type that vector.size() returns.

+      if (arg_names[i] == "wmode") {
+        if (arg_values[i] == "direct" || arg_values[i] == "gpu")
+          needsgpu = true;
+        break;
+      }
+    }
+    UMA_HISTOGRAM_ENUMERATION("Flash.UsesGPU",

[brettw, 2012/08/27 22:19:28]

Can you add a comment here about what this histogram contains? The way you're
using it to communicate capabilities is "nontraditional" :)

+        needsgpu * 2 + prefs.is_webgl_supported, 4);

[vangelis, 2012/08/28 05:12:06]

Is this bool to int conversion pretty standard and supported the same way across
all platforms? 

+  }
+#endif
+
   argn_ = arg_names;
   argv_ = arg_values;
   scoped_array<const char*> argn_array(StringVectorToArgArray(argn_));