Add UMA metrics for measuring number of coalesed events and their latency.

ui/base/x/x11_util.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file defines utility functions for X11 (Linux only). This code has been
 // ported from XCB since we can't use XCB on Ubuntu while its 32-bit support
 // remains woefully incomplete.
 
 #include "ui/base/x/x11_util.h"
 
@@ skipping 10 matching lines @@
 #include <X11/extensions/shape.h>
 #include <X11/extensions/XInput2.h>
 #include <X11/extensions/Xrandr.h>
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/singleton.h"
 #include "base/message_loop.h"
+#include "base/metrics/histogram.h"
 #include "base/string_number_conversions.h"
 #include "base/string_util.h"
 #include "base/stringprintf.h"
 #include "base/sys_byteorder.h"
 #include "base/threading/thread.h"
 #include "ui/base/events/event_utils.h"
 #include "ui/base/keycodes/keyboard_code_conversion_x.h"
 #include "ui/base/touch/touch_factory_x11.h"
 #include "ui/base/x/valuators.h"
 #include "ui/base/x/x11_util_internal.h"
@@ skipping 581 matching lines @@
         XGetEventData(display, &last_event->xcookie);
         ++num_coalesed;
         continue;
       } else {
         // This isn't an event we want so free its cookie data.
         XFreeEventData(display, &next_event.xcookie);
       }
     }
     break;
   }
+
+  if (num_coalesed > 0) {
+    base::TimeDelta delta = ui::EventTimeFromNative(last_event) -
+        ui::EventTimeFromNative(const_cast<XEvent*>(xev));
+    if (event_type == XI_Motion) {
+      UMA_HISTOGRAM_COUNTS_10000("Event.CoalescedCount.Mouse", num_coalesed);
+      UMA_HISTOGRAM_TIMES("Event.CoalescedLatency.Mouse", delta);
+    } else {
+#if defined(USE_XI2_MT)
+      DCHECK(event_type == XI_TouchUpdate);

[sadrul, 2013/04/05 23:27:09]

DCHECK_EQ

[varunjain, 2013/04/08 14:37:12]

Done.

+#endif
+      UMA_HISTOGRAM_COUNTS_10000("Event.CoalescedCount.Touch", num_coalesed);
+      UMA_HISTOGRAM_TIMES("Event.CoalescedLatency.Touch", delta);
+    }
+  }
   return num_coalesed;
 }
 #endif
 
 void HideHostCursor() {
   CR_DEFINE_STATIC_LOCAL(XScopedCursor, invisible_cursor,
                          (CreateInvisibleCursor(), ui::GetXDisplay()));
   XDefineCursor(ui::GetXDisplay(), DefaultRootWindow(ui::GetXDisplay()),
                 invisible_cursor.get());
 }
@@ skipping 1152 matching lines @@
       << "request_code " << static_cast<int>(error_event.request_code) << ", "
       << "minor_code " << static_cast<int>(error_event.minor_code)
       << " (" << request_str << ")";
 }
 
 // ----------------------------------------------------------------------------
 // End of x11_util_internal.h
 
 
 }  // namespace ui