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..3b813034c9ae7dcf9b921d4f0d651b0457a214df 100644
--- a/content/browser/renderer_host/render_process_host_impl.cc
+++ b/content/browser/renderer_host/render_process_host_impl.cc
@@ -967,7 +967,9 @@ bool RenderProcessHostImpl::Init() {
     // As long as there's no renderer prefix, we can use the zygote process
     // at this stage.
     child_process_launcher_.reset(new ChildProcessLauncher(
-        new RendererSandboxedProcessLauncherDelegate(channel_.get()), cmd_line,
+        new RendererSandboxedProcessLauncherDelegate(channel_.get()),
+        field_trial_state_.get(),
+        cmd_line,
         GetID(), this, child_token_,
         base::Bind(&RenderProcessHostImpl::OnMojoError,
                    weak_factory_.GetWeakPtr(),
@@ -1587,7 +1589,7 @@ 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 +1628,7 @@ 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 +1841,13 @@ void RenderProcessHostImpl::PropagateBrowserCommandLineToRenderer(
   renderer_cmd->CopySwitchesFrom(browser_cmd, kSwitchNames,
                                  arraysize(kSwitchNames));
 
+#if defined(OS_WIN)

[Alexei Svitkine (slow), 2016/10/03 15:28:05]

I think you can just ifdef the line below and have
CopyFeatureAndFieldTrialFlags() be called with both parameters on all platforms.
That function could then check if the shared memory is null or not to do the new
logic.

[lawrencewu, 2016/10/03 21:36:11]

Done.

+  field_trial_state_.reset(new base::SharedMemory());
+  BrowserChildProcessHostImpl::CopyFeatureAndFieldTrialFlags(
+    renderer_cmd, field_trial_state_.get());
+#else
   BrowserChildProcessHostImpl::CopyFeatureAndFieldTrialFlags(renderer_cmd);
+#endif
 
   if (browser_cmd.HasSwitch(switches::kTraceStartup) &&
       BrowserMainLoop::GetInstance()->is_tracing_startup_for_duration()) {