Flush stability file after initialization

chrome/browser/chrome_browser_field_trials_desktop.cc

 // Copyright 2013 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/chrome_browser_field_trials_desktop.h"
 
 #if defined(OS_WIN)
 #include <windows.h>
 #endif
 
@@ skipping 157 matching lines @@
     global_data.SetString(browser_watcher::kStabilitySpecialBuild,
                           special_build);
 #if defined(ARCH_CPU_X86)
     global_data.SetString(browser_watcher::kStabilityPlatform, "Win32");
 #elif defined(ARCH_CPU_X86_64)
     global_data.SetString(browser_watcher::kStabilityPlatform, "Win64");
 #endif
 
     // Record information about chrome's module. We want this to be done early.
     RecordChromeModuleInfo(global_tracker);
+
+    // Trigger a flush of the memory mapped file to maximize the chances of
+    // having a minimal amount of content in the stability file, even if
+    // the system crashes or loses power. Note: this does not flush the file
+    // metadata nor does it wait for the changes to be flushed to disk before
+    // returning.
+    ::FlushViewOfFile(global_tracker->allocator()->data(), 0U);

[bcwhite, 2017/03/06 13:59:17]

How about making this a method off of GlobalActivityTracker so it can be
cross-platform and reusable.

Perhaps with a boolean "synchronous" flag that waits for the flush?

[manzagop (departed), 2017/03/06 16:46:26]

I guess GlobalActivityTracker would have a flush that calls to the allocator's
flush that only has an effect if it's a FilePersistentMemoryAllocator? And the
actual flushing would be in base::MemoryMappedFile?

If you agree, maybe we can start with this and in parallel, have another CL to
add flushing to base::MemoryMappedFile?

[bcwhite, 2017/03/07 18:37:26]

Yeah...  It would have to be a virtual method on the PMA.  Best to do that in a
different CL.  I'll look into it.

   }
 }
 #endif  // defined(OS_WIN)
 
 }  // namespace
 
 void SetupDesktopFieldTrials() {
   prerender::ConfigurePrerender();
   SetupStunProbeTrial();
 #if defined(OS_WIN)
   SetupStabilityDebugging();
   base::FeatureList::IsEnabled(features::kModuleDatabase);
 #endif  // defined(OS_WIN)
   // Activate the experiment as early as possible to increase its visibility
   // (e.g. the likelihood of its presence in the serialized system profile).
   // This also needs to happen before the browser rendez-vous attempt
   // (NotifyOtherProcessOrCreate) in PreMainMessageLoopRun so the corresponding
   // metrics are tagged.
   base::FeatureList::IsEnabled(features::kDesktopFastShutdown);
 }
 
 }  // namespace chrome