Construct a field trial to see if HIGH or MEDIUM memory model "works better"...

chrome/browser/render_widget_host_view_win.cc

 // Copyright (c) 2006-2008 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.
 
 #include "chrome/browser/render_widget_host_view_win.h"
 
 #include "base/command_line.h"
 #include "base/gfx/gdi_util.h"
 #include "base/gfx/rect.h"
 #include "base/histogram.h"
 #include "base/win_util.h"
 #include "chrome/browser/browser_accessibility.h"
 #include "chrome/browser/browser_accessibility_manager.h"
+#include "chrome/browser/browser_trial.h"
 #include "chrome/browser/render_process_host.h"
 // TODO(beng): (Cleanup) we should not need to include this file... see comment
 //             in |DidBecomeSelected|.
 #include "chrome/browser/render_view_host.h"
 #include "chrome/browser/render_widget_host.h"
 #include "chrome/common/chrome_constants.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/l10n_util.h"
 #include "chrome/common/plugin_messages.h"
 #include "chrome/common/win_util.h"
@@ skipping 402 matching lines @@
     if (damaged_rect.bottom() > bitmap_rect.bottom()) {
       RECT r;
       r.left = damaged_rect.x();
       r.right = damaged_rect.right();
       r.top = std::max(bitmap_rect.bottom(), damaged_rect.y());
       r.bottom = damaged_rect.bottom();
       paint_dc.FillRect(&r, white_brush);
     }
     if (!whiteout_start_time_.is_null()) {
       TimeDelta whiteout_duration = TimeTicks::Now() - whiteout_start_time_;
-      UMA_HISTOGRAM_TIMES(L"MPArch.RWHH_WhiteoutDuration", whiteout_duration);
+
+      // If field trial is active, report results in special histogram.
+      static scoped_refptr<FieldTrial> trial(
+          FieldTrialList::Find(BrowserTrial::kMemoryModelFieldTrial));
+      if (trial.get()) {
+        if (trial->boolean_value())
+          UMA_HISTOGRAM_TIMES(L"MPArch.RWHH_WhiteoutDuration_trial_high_memory",
+                              whiteout_duration);
+        else
+          UMA_HISTOGRAM_TIMES(L"MPArch.RWHH_WhiteoutDuration_trial_med_memory",
+                              whiteout_duration);
+      } else {
+        UMA_HISTOGRAM_TIMES(L"MPArch.RWHH_WhiteoutDuration", whiteout_duration);
+      }
+
       // Reset the start time to 0 so that we start recording again the next
       // time the backing store is NULL...
       whiteout_start_time_ = TimeTicks();
     }
   } else {
     paint_dc.FillRect(&paint_dc.m_ps.rcPaint, white_brush);
     if (whiteout_start_time_.is_null())
       whiteout_start_time_ = TimeTicks::Now();
   }
 }
@@ skipping 438 matching lines @@
     ::DestroyWindow(tooltip_hwnd_);
   tooltip_hwnd_ = NULL;
 }
 
 void RenderWidgetHostViewWin::ShutdownHost() {
   shutdown_factory_.RevokeAll();
   render_widget_host_->Shutdown();
   // Do not touch any members at this point, |this| has been deleted.
 }