Adding a field trial for testing --force-compositing-mode on 50% of

chrome/browser/chrome_browser_main.h

 // 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.
 
 #ifndef CHROME_BROWSER_CHROME_BROWSER_MAIN_H_
 #define CHROME_BROWSER_CHROME_BROWSER_MAIN_H_
 #pragma once
 
 #include "base/basictypes.h"
 #include "base/gtest_prod_util.h"
@@ skipping 34 matching lines @@
 struct MainFunctionParams;
 }
 
 class ChromeBrowserMainParts : public content::BrowserMainParts {
  public:
   virtual ~ChromeBrowserMainParts();
 
   // Add additional ChromeBrowserMainExtraParts.
   virtual void AddParts(ChromeBrowserMainExtraParts* parts);
 
+  static bool in_force_compositing_mode_trial() {
+    return in_force_compositing_mode_trial_;
+  }

[Ilya Sherman, 2012/06/06 22:31:51]

Do we really need to cache this, rather than querying it from FieldTrialList?  I
suspect that we shouldn't be adding any new methods to the public interface for
ChromeBrowserMainParts...

[vangelis, 2012/06/06 23:44:44]

I removed the public method and replaced it with a global.. This is inline with
what some of the other field trials are actually doing.  Regarding caching, I
only see two options:

1. Cache the group value
2. Expose the name of the trial and the enable group and query every time I need
the value.

Either way we end up with some global data that needs to be exposed across
files.  #1 eliminates unnecessary dictionary searches so it seems better.

I'm open to other suggestions though.

[Ilya Sherman, 2012/06/07 05:27:24]

I'd prefer #2, as it only requires global /constants/, which are a different
animal altogether from global variables.  If you strongly prefer a cached
global, though, I would at least recommend defining it in a separate header -- I
don't think this CL ought to change any publicly exported state in
chrome_browser_main.h.

+
  protected:
   explicit ChromeBrowserMainParts(
       const content::MainFunctionParams& parameters);
 
   // content::BrowserMainParts overrides.
   // These are called in-order by content::BrowserMainLoop.
   // Each stage calls the same stages in any ChromeBrowserMainExtraParts added
   // with AddParts() from ChromeContentBrowserClient::CreateBrowserMainParts.
   virtual void PreEarlyInitialization() OVERRIDE;
   virtual void PostEarlyInitialization() OVERRIDE;
@@ skipping 57 matching lines @@
   // has on retention and general apps/webstore usage.
   void DefaultAppsFieldTrial();
 
   // A field trial to see what effects launching Chrome automatically on
   // computer startup has on retention and usage of Chrome.
   void AutoLaunchChromeFieldTrial();
 
   // Field trial for testing domain bound certs.
   void DomainBoundCertsFieldTrial();
 
+  // Field trial for testing compositing on all pages.
+  void ForceCompositingModeFieldTrial();
+
   // A collection of field trials intended to test the uniformity and
   // correctness of the field trial control, bucketing and reporting systems.
   void SetupUniformityFieldTrials();
 
   // Methods for |SetupMetricsAndFieldTrials()| --------------------------------
 
   // Constructs metrics service and does related initialization, including
   // creation of field trials. Call only after labs have been converted to
   // switches.
   void SetupMetricsAndFieldTrials();
@@ skipping 66 matching lines @@
   PrefService* local_state_;
   FilePath user_data_dir_;
 
   // Members needed across shutdown methods.
   bool restart_last_session_;
 
   // Tests can set this to true to disable restricting cookie access in the
   // network stack, as this can only be done once.
   static bool disable_enforcing_cookie_policies_for_tests_;
 
+  // Set to true if the force-compositing-mode trial has been enabled for
+  // this client.
+  static bool in_force_compositing_mode_trial_;
+
   friend class BrowserMainTest;
   FRIEND_TEST_ALL_PREFIXES(BrowserMainTest,
                            WarmConnectionFieldTrial_WarmestSocket);
   FRIEND_TEST_ALL_PREFIXES(BrowserMainTest, WarmConnectionFieldTrial_Random);
   FRIEND_TEST_ALL_PREFIXES(BrowserMainTest, WarmConnectionFieldTrial_Invalid);
   DISALLOW_COPY_AND_ASSIGN(ChromeBrowserMainParts);
 };
 
 // Records the conditions that can prevent Breakpad from generating and
 // sending crash reports.  The presence of a Breakpad handler (after
 // attempting to initialize crash reporting) and the presence of a debugger
 // are registered with the UMA metrics service.
 void RecordBreakpadStatusUMA(MetricsService* metrics);
 
 // Displays a warning message if some minimum level of OS support is not
 // present on the current platform.
 void WarnAboutMinimumSystemRequirements();
 
 // Records the time from our process' startup to the present time in
 // the UMA histogram |metric_name|.
 void RecordBrowserStartupTime();
 
 // Records a time value to an UMA histogram in the context of the
 // PreReadExperiment field-trial. This also reports to the appropriate
 // sub-histogram (_PreRead(Enabled|Disabled)).
 void RecordPreReadExperimentTime(const char* name, base::TimeDelta time);
 
 #endif  // CHROME_BROWSER_CHROME_BROWSER_MAIN_H_