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 950 matching lines @@
     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,
-        GetID(), this, child_token_,
+        GetID(), this, field_trial_state_.get(), 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
   // process is still launching, the channel will be paused and outgoing
@@ skipping 598 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));
 
-  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()) {
     // 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