Fixed the Touchscreen.TouchEventsEnabled histogram to record the correct values on X11 and Ozone ba…

chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.cc

Index: chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.cc
diff --git a/chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.cc b/chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.cc
index 3680ad957d6ce1a913d5c6a374e9ab86f5a7d0dd..240eeb6be8d46bfd870041b5990d5aeabd2b78e2 100644
--- a/chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.cc
+++ b/chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.cc
@@ -23,6 +23,7 @@
 #include "content/public/browser/browser_thread.h"
 #include "ui/base/touch/touch_device.h"
 #include "ui/base/ui_base_switches.h"
+#include "ui/events/devices/device_data_manager.h"
 #include "ui/events/event_switches.h"
 #include "ui/gfx/screen.h"
 
@@ -236,7 +237,6 @@ void RecordTouchEventState() {
     NOTREACHED();
     return;
   }

[Ilya Sherman, 2015/06/24 23:46:50]

nit: Please revert the change to this line (i.e. restore the newline below it).

[bruthig, 2015/06/25 17:26:52]

Done.

-
   UMA_HISTOGRAM_ENUMERATION("Touchscreen.TouchEventsEnabled", state,
                             UMA_TOUCH_EVENTS_STATE_COUNT);
 }
@@ -250,6 +250,9 @@ ChromeBrowserMainExtraPartsMetrics::ChromeBrowserMainExtraPartsMetrics()
 ChromeBrowserMainExtraPartsMetrics::~ChromeBrowserMainExtraPartsMetrics() {
   if (is_screen_observer_)
     gfx::Screen::GetNativeScreen()->RemoveObserver(this);
+#if defined(USE_OZONE) || defined(USE_X11)
+  ui::DeviceDataManager::GetInstance()->RemoveObserver(this);

[Ilya Sherman, 2015/06/24 23:46:50]

Is it safe to call RemoveObserver() even if |this| is not currently registered
as an observer?

[bruthig, 2015/06/25 17:26:51]

That path is executed by the tests so I assume it is.

+#endif  // defined(USE_OZONE) || defined(USE_X11)
 }
 
 void ChromeBrowserMainExtraPartsMetrics::PreProfileInit() {
@@ -269,7 +272,18 @@ void ChromeBrowserMainExtraPartsMetrics::PostBrowserStart() {
                             GetLinuxWindowManager(),
                             UMA_LINUX_WINDOW_MANAGER_COUNT);
 #endif
+
+#if defined(USE_OZONE) || defined(USE_X11)
+  // The touch event state for X11 and Ozone based event sub-systems are based
+  // on device scans that happen asynchronously. So we may need to attach an
+  // observer to wait until these scans complete.
+  if (ui::DeviceDataManager::GetInstance()->device_lists_complete())
+    OnDeviceListsComplete();
+  else
+    ui::DeviceDataManager::GetInstance()->AddObserver(this);
+#else
   RecordTouchEventState();
+#endif  // defined(USE_OZONE) || defined(USE_X11)
 
 #if defined(OS_MACOSX) && !defined(OS_IOS)
   RecordMacMetrics();
@@ -311,6 +325,11 @@ void ChromeBrowserMainExtraPartsMetrics::ProfilerFinishedCollectingMetrics() {
   first_web_contents_profiler_.reset();
 }
 
+void ChromeBrowserMainExtraPartsMetrics::OnDeviceListsComplete() {
+  ui::DeviceDataManager::GetInstance()->RemoveObserver(this);
+  RecordTouchEventState();
+}
+
 void ChromeBrowserMainExtraPartsMetrics::EmitDisplaysChangedMetric() {
   int display_count = gfx::Screen::GetNativeScreen()->GetNumDisplays();
   if (display_count != display_count_) {