Revert "Always activate MojoApplicationHost"

This reverts commit bd0aa4dc.

TBR=darin@chromium.org
BUG=415059

Review URL: https://codereview.chromium.org/584173002

Cr-Commit-Position: refs/heads/master@{#295799}

content/browser/frame_host/render_frame_host_impl.cc

@@ -287,6 +287,7 @@ RenderViewHost* RenderFrameHostImpl::GetRenderViewHost() {
 }
 
 ServiceRegistry* RenderFrameHostImpl::GetServiceRegistry() {
+  static_cast<RenderProcessHostImpl*>(GetProcess())->EnsureMojoActivated();
   return &service_registry_;
 }
 

content/browser/mojo/mojo_application_host.cc

@@ -47,7 +47,7 @@ bool MojoApplicationHost::Init() {
   return true;
 }
 
-void MojoApplicationHost::Activate(IPC::Sender* sender,
+bool MojoApplicationHost::Activate(IPC::Sender* sender,
                                    base::ProcessHandle process_handle) {
   DCHECK(!did_activate_);
   DCHECK(client_handle_.is_valid());
@@ -56,6 +56,7 @@ void MojoApplicationHost::Activate(IPC::Sender* sender,
       PlatformFileFromScopedPlatformHandle(client_handle_.Pass());
   did_activate_ = sender->Send(new MojoMsg_Activate(
       IPC::GetFileHandleForProcess(client_file, process_handle, true)));
+  return did_activate_;
 }
 
 void MojoApplicationHost::WillDestroySoon() {

content/browser/mojo/mojo_application_host.h

@@ -30,10 +30,12 @@ class MojoApplicationHost {
   //  1- Init makes service_registry() available synchronously.
   //  2- Activate establishes the actual connection to the peer process.
   bool Init();
-  void Activate(IPC::Sender* sender, base::ProcessHandle process_handle);
+  bool Activate(IPC::Sender* sender, base::ProcessHandle process_handle);
 
   void WillDestroySoon();
 
+  bool did_activate() const { return did_activate_; }
+
   ServiceRegistry* service_registry() { return &service_registry_; }
 
  private:

content/browser/renderer_host/render_process_host_impl.cc

@@ -437,6 +437,7 @@ RenderProcessHostImpl::RenderProcessHostImpl(
 #endif
       pending_views_(0),
       mojo_application_host_(new MojoApplicationHost),
+      mojo_activation_required_(false),
       visible_widgets_(0),
       backgrounded_(true),
       is_initialized_(false),
@@ -641,6 +642,20 @@ bool RenderProcessHostImpl::Init() {
   return true;
 }
 
+void RenderProcessHostImpl::MaybeActivateMojo() {
+  // TODO(darin): Following security review, we can unconditionally initialize
+  // Mojo in all renderers. We will then be able to directly call Activate()
+  // from OnProcessLaunched.
+  if (!mojo_activation_required_)
+    return;  // Waiting on someone to require Mojo.
+
+  if (!GetHandle())
+    return;  // Waiting on renderer startup.
+
+  if (!mojo_application_host_->did_activate())
+    mojo_application_host_->Activate(this, GetHandle());
+}
+
 bool RenderProcessHostImpl::ShouldUseMojoChannel() const {
   const base::CommandLine& command_line =
       *base::CommandLine::ForCurrentProcess();
@@ -1911,6 +1926,7 @@ void RenderProcessHostImpl::ProcessDied(bool already_dead) {
   }
 
   mojo_application_host_.reset(new MojoApplicationHost);
+  mojo_activation_required_ = false;
 
   // It's possible that one of the calls out to the observers might have caused
   // this object to be no longer needed.
@@ -2077,7 +2093,7 @@ void RenderProcessHostImpl::OnProcessLaunched() {
   // Allow Mojo to be setup before the renderer sees any Chrome IPC messages.
   // This way, Mojo can be safely used from the renderer in response to any
   // Chrome IPC message.
-  mojo_application_host_->Activate(this, GetHandle());
+  MaybeActivateMojo();
 
   while (!queued_messages_.empty()) {
     Send(queued_messages_.front());
@@ -2218,4 +2234,9 @@ void RenderProcessHostImpl::DecrementWorkerRefCount() {
     Cleanup();
 }
 
+void RenderProcessHostImpl::EnsureMojoActivated() {
+  mojo_activation_required_ = true;
+  MaybeActivateMojo();
+}
+
 }  // namespace content

content/browser/renderer_host/render_process_host_impl.h

@@ -252,6 +252,9 @@ class CONTENT_EXPORT RenderProcessHostImpl
   // immediately after receiving response headers.
   void ResumeResponseDeferredAtStart(const GlobalRequestID& request_id);
 
+  // Activates Mojo for this process. Does nothing if Mojo is already activated.
+  void EnsureMojoActivated();
+
  protected:
   // A proxy for our IPC::Channel that lives on the IO thread (see
   // browser_process.h)
@@ -276,6 +279,7 @@ class CONTENT_EXPORT RenderProcessHostImpl
  private:
   friend class VisitRelayingRenderProcessHost;
 
+  void MaybeActivateMojo();
   bool ShouldUseMojoChannel() const;
   scoped_ptr<IPC::ChannelProxy> CreateChannelProxy(
       const std::string& channel_id);
@@ -323,6 +327,7 @@ class CONTENT_EXPORT RenderProcessHostImpl
 #endif
 
   scoped_ptr<MojoApplicationHost> mojo_application_host_;
+  bool mojo_activation_required_;
 
   // The registered IPC listener objects. When this list is empty, we should
   // delete ourselves.