Move command handling and updating off Browser and onto a helper object.

chrome/browser/command_updater.cc

Index: chrome/browser/command_updater.cc
===================================================================
--- chrome/browser/command_updater.cc	(revision 144216)
+++ chrome/browser/command_updater.cc	(working copy)
@@ -40,18 +40,21 @@
   return commands_.find(id) != commands_.end();
 }
 
-void CommandUpdater::ExecuteCommand(int id) {
-  ExecuteCommandWithDisposition(id, CURRENT_TAB);
+bool CommandUpdater::ExecuteCommand(int id) {
+  return ExecuteCommandWithDisposition(id, CURRENT_TAB);
 }
 
-void CommandUpdater::ExecuteCommandWithDisposition(
+bool CommandUpdater::ExecuteCommandWithDisposition(
     int id,
     WindowOpenDisposition disposition) {
-  if (IsCommandEnabled(id))
+  if (SupportsCommand(id) && IsCommandEnabled(id)) {
     delegate_->ExecuteCommandWithDisposition(id, disposition);
+    return true;
+  }
+  return false;
 }
 
-CommandUpdater::CommandObserver::~CommandObserver() {
+CommandObserver::~CommandObserver() {
 }
 
 void CommandUpdater::UpdateCommandEnabled(int id, bool enabled) {