Convert ChromeViewMsg_SetFieldTrialGroup to use mojo.

chrome/renderer/chrome_render_thread_observer.h

Index: chrome/renderer/chrome_render_thread_observer.h
diff --git a/chrome/renderer/chrome_render_thread_observer.h b/chrome/renderer/chrome_render_thread_observer.h
index bbc85bd6f133bbf73767dc1c55bfac66f4d5e238..7594db33a3fd523b741aaf2d85d9f09f4e47b81c 100644
--- a/chrome/renderer/chrome_render_thread_observer.h
+++ b/chrome/renderer/chrome_render_thread_observer.h
@@ -12,6 +12,7 @@
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "base/metrics/field_trial.h"
+#include "chrome/common/field_trial.mojom.h"
 #include "chrome/common/renderer_configuration.mojom.h"
 #include "components/content_settings/core/common/content_settings.h"
 #include "components/variations/child_process_field_trial_syncer.h"
@@ -32,6 +33,7 @@ class VisitedLinkSlave;
 // observer.
 class ChromeRenderThreadObserver : public content::RenderThreadObserver,
                                    public base::FieldTrialList::Observer,
+                                   public chrome::mojom::FieldTrialGroupSetter,
                                    public chrome::mojom::RendererConfiguration {
  public:
   ChromeRenderThreadObserver();
@@ -53,24 +55,26 @@ class ChromeRenderThreadObserver : public content::RenderThreadObserver,
       content::AssociatedInterfaceRegistry* associated_interfaces) override;
   void UnregisterMojoInterfaces(
       content::AssociatedInterfaceRegistry* associated_interfaces) override;
-  bool OnControlMessageReceived(const IPC::Message& message) override;
   void OnRenderProcessShutdown() override;
 
   // base::FieldTrialList::Observer:
   void OnFieldTrialGroupFinalized(const std::string& trial_name,
                                   const std::string& group_name) override;
 
+  // chrome::mojom::FieldTrialGroupSetter:
+  void SetFieldTrialGroup(const std::string& trial_name,
+                          const std::string& group_name) override;
+
   // chrome::mojom::RendererConfiguration:
   void SetInitialConfiguration(bool is_incognito_process) override;
   void SetContentSettingRules(
       const RendererContentSettingRules& rules) override;
 
+  void OnFieldTrialGroupSetterAssociatedRequest(
+      chrome::mojom::FieldTrialGroupSetterAssociatedRequest request);
   void OnRendererConfigurationAssociatedRequest(
       chrome::mojom::RendererConfigurationAssociatedRequest request);
 
-  void OnSetFieldTrialGroup(const std::string& trial_name,
-                            const std::string& group_name);
-
   static bool is_incognito_process_;
   std::unique_ptr<content::ResourceDispatcherDelegate> resource_delegate_;
   RendererContentSettingRules content_setting_rules_;
@@ -78,6 +82,8 @@ class ChromeRenderThreadObserver : public content::RenderThreadObserver,
 
   std::unique_ptr<visitedlink::VisitedLinkSlave> visited_link_slave_;
 
+  mojo::AssociatedBindingSet<chrome::mojom::FieldTrialGroupSetter>
+      field_trial_group_setter_bindings_;
   mojo::AssociatedBindingSet<chrome::mojom::RendererConfiguration>
       renderer_configuration_bindings_;