cc: Allow sending BeginMainFrame before draw or activation

cc/base/switches.cc

Index: cc/base/switches.cc
diff --git a/cc/base/switches.cc b/cc/base/switches.cc
index 7e45074030db420352e32bc3aeea30964b39b51c..5f98989782130e0f91be0c32eefe5c5fbb7a0ffb 100644
--- a/cc/base/switches.cc
+++ b/cc/base/switches.cc
@@ -33,6 +33,22 @@ const char kEnableLCDText[] = "enable-lcd-text";
 // Paint content on the compositor thread instead of the main thread.
 const char kEnableImplSidePainting[] = "enable-impl-side-painting";
 
+// Disables the starting the next commit before the previous commit has drawn.
+// Overrides the kEnableStartCommitBeforeDraw flag.
+const char kDisableStartCommitBeforeDraw[] = "disable-start-commit-before-draw";
+
+// Allows the next commit to start before the previous commit has drawn.
+const char kEnableStartCommitBeforeDraw[] = "enable-start-commit-before-draw";
+
+// Disables the starting the next commit before the previous commit activates.
+// Overrides the kEnableStartCommitBeforeDraw flag.
+const char kDisableStartCommitBeforeActivate[] =
+    "disable-start-commit-before-activate";
+
+// Allows the next commit to start before the previous commit activates.
+const char kEnableStartCommitBeforeActivate[] =
+    "enable-start-commit-before-activate";
+
 const char kEnableTopControlsPositionCalculation[] =
     "enable-top-controls-position-calculation";
 
@@ -206,5 +222,32 @@ bool IsMapImageEnabled() {
   return false;
 }
 
+bool IsStartCommitBeforeDrawEnabled() {
+  // Starting the commit before activation implies starting the commit
+  // before draw as well.
+  if (IsStartCommitBeforeActivateEnabled())
+    return true;
+
+  const CommandLine& command_line = *CommandLine::ForCurrentProcess();
+
+  if (command_line.HasSwitch(switches::kDisableStartCommitBeforeDraw))
+    return false;
+  else if (command_line.HasSwitch(switches::kEnableStartCommitBeforeDraw))
+    return true;
+
+  return true;
+}
+
+bool IsStartCommitBeforeActivateEnabled() {
+  const CommandLine& command_line = *CommandLine::ForCurrentProcess();
+
+  if (command_line.HasSwitch(switches::kDisableStartCommitBeforeActivate))
+    return false;
+  else if (command_line.HasSwitch(switches::kEnableStartCommitBeforeActivate))
+    return true;
+
+  return false;
+}
+
 }  // namespace switches
 }  // namespace cc