Initial implementation for sharing field trial state (win)

content/browser/renderer_host/render_process_host_impl.cc

 // Copyright 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.
 
 // Represents the browser side of the browser <--> renderer communication
 // channel. There will be one RenderProcessHost per renderer process.
 
 #include "content/browser/renderer_host/render_process_host_impl.h"
 
 #include <algorithm>
@@ skipping 949 matching lines @@
     base::CommandLine* cmd_line = new base::CommandLine(renderer_path);
     if (!renderer_prefix.empty())
       cmd_line->PrependWrapper(renderer_prefix);
     AppendRendererCommandLine(cmd_line);
     cmd_line->AppendSwitchASCII(switches::kProcessChannelID, channel_id);
 
     // Spawn the child process asynchronously to avoid blocking the UI thread.
     // 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(),
                    base::ThreadTaskRunnerHandle::Get())));
     channel_->Pause();
 
     fast_shutdown_started_ = false;
   }
 
   // Push any pending messages to the channel now. Note that if the child
@@ skipping 599 matching lines @@
   gpu_data_manager->AppendRendererCommandLine(command_line);
 
   // Slimming Paint v2 implies layer lists in the renderer.
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kEnableSlimmingPaintV2)) {
     command_line->AppendSwitch(cc::switches::kEnableLayerLists);
   }
 }
 
 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);
 
 #if defined(OS_WIN)
   command_line->AppendArg(switches::kPrefetchArgumentRenderer);
 #endif  // defined(OS_WIN)
 
   // Now send any options from our own command line we want to propagate.
   const base::CommandLine& browser_command_line =
@@ skipping 18 matching lines @@
 #endif
 
   AppendCompositorCommandLineFlags(command_line);
 
   command_line->AppendSwitchASCII(switches::kMojoApplicationChannelToken,
                                   mojo_child_connection_->service_token());
 }
 
 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[] = {
     switches::kAgcStartupMinVolume,
     switches::kAecRefinedAdaptiveFilter,
     switches::kAllowLoopbackInPeerConnection,
     switches::kAndroidFontsPath,
     switches::kAudioBufferSize,
     switches::kBlinkSettings,
     switches::kDefaultTileWidth,
@@ skipping 192 matching lines @@
 #endif
 #if defined(ENABLE_IPC_FUZZER)
     switches::kIpcDumpDirectory,
     switches::kIpcFuzzerTestcase,
 #endif
     switches::kUseMusInRenderer,
   };
   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()) {
     // Pass kTraceStartup switch to renderer only if startup tracing has not
     // finished.
     renderer_cmd->AppendSwitchASCII(
         switches::kTraceStartup,
         browser_cmd.GetSwitchValueASCII(switches::kTraceStartup));
   }
 
@@ skipping 1187 matching lines @@
   LOG(ERROR) << "Terminating render process for bad Mojo message: " << error;
 
   // The ReceivedBadMessage call below will trigger a DumpWithoutCrashing. Alias
   // enough information here so that we can determine what the bad message was.
   base::debug::Alias(&error);
   bad_message::ReceivedBadMessage(process.get(),
                                   bad_message::RPH_MOJO_PROCESS_ERROR);
 }
 
 }  // namespace content