Initial implementation for sharing field trial state (win)

content/browser/renderer_host/render_process_host_impl.cc

Index: content/browser/renderer_host/render_process_host_impl.cc
diff --git a/content/browser/renderer_host/render_process_host_impl.cc b/content/browser/renderer_host/render_process_host_impl.cc
index 00f88e99958af2563e24f2a1e09c9d1f1b39263c..27036fac22aa1b1e81018e064b28dcd135bccad9 100644
--- a/content/browser/renderer_host/render_process_host_impl.cc
+++ b/content/browser/renderer_host/render_process_host_impl.cc
@@ -968,7 +968,7 @@ bool RenderProcessHostImpl::Init() {
     // at this stage.
     child_process_launcher_.reset(new ChildProcessLauncher(
         new RendererSandboxedProcessLauncherDelegate(channel_.get()), cmd_line,
-        GetID(), this, child_token_,
+        GetID(), this, field_trial_state_.get(), child_token_,
         base::Bind(&RenderProcessHostImpl::OnMojoError,
                    weak_factory_.GetWeakPtr(),
                    base::ThreadTaskRunnerHandle::Get())));
@@ -1587,7 +1587,7 @@ static void AppendCompositorCommandLineFlags(base::CommandLine* command_line) {
 }
 
 void RenderProcessHostImpl::AppendRendererCommandLine(
-    base::CommandLine* command_line) const {
+    base::CommandLine* command_line) {
   // Pass the process type first, so it shows first in process listings.
   command_line->AppendSwitchASCII(switches::kProcessType,
                                   switches::kRendererProcess);
@@ -1626,7 +1626,7 @@ void RenderProcessHostImpl::AppendRendererCommandLine(
 
 void RenderProcessHostImpl::PropagateBrowserCommandLineToRenderer(
     const base::CommandLine& browser_cmd,
-    base::CommandLine* renderer_cmd) const {
+    base::CommandLine* renderer_cmd) {
   // Propagate the following switches to the renderer command line (along
   // with any associated values) if present in the browser command line.
   static const char* const kSwitchNames[] = {
@@ -1839,7 +1839,17 @@ void RenderProcessHostImpl::PropagateBrowserCommandLineToRenderer(
   renderer_cmd->CopySwitchesFrom(browser_cmd, kSwitchNames,
                                  arraysize(kSwitchNames));
 
-  BrowserChildProcessHostImpl::CopyFeatureAndFieldTrialFlags(renderer_cmd);
+#if defined(OS_WIN)
+  if (base::FeatureList::IsEnabled(
+          features::kShareFieldTrialStateViaSharedMemory))
+    field_trial_state_.reset(new base::SharedMemory());

[Alexei Svitkine (slow), 2016/10/04 18:49:36]

I don't like duplicating this code - especially since it has to have ifdefs.

Instead, pass a pointer to the scoped ptr to the function, so it can do the
.reset() itself.

e.g.

BrowserChildProcessHostImpl::CopyFeatureAndFieldTrialFlags(renderer_cmd,
&field_trial_state_);

[lawrencewu, 2016/10/05 20:57:56]

Done.

+#endif
+  BrowserChildProcessHostImpl::CopyFeatureAndFieldTrialFlags(
+      renderer_cmd, field_trial_state_.get());
+#if defined(OS_WIN)
+  if (!field_trial_state_.get()->handle().GetHandle())
+    field_trial_state_.reset();
+#endif
 
   if (browser_cmd.HasSwitch(switches::kTraceStartup) &&
       BrowserMainLoop::GetInstance()->is_tracing_startup_for_duration()) {