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 6c58f0ce90016cfb6afc3b4eead5eb6a9e7f91a4..14a4b71ae215ccb423b6f7304c4581db5c5d2481 100644
--- a/cc/base/switches.cc
+++ b/cc/base/switches.cc
@@ -37,6 +37,22 @@ const char kDisableDeadlineScheduling[] = "disable-deadline-scheduling";
 // of less than 1 vsync if their intervals are properly nested.
 const char kEnableDeadlineScheduling[] = "enable-deadline-scheduling";
 
+// 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";
 
@@ -186,5 +202,41 @@ bool IsDeadlineSchedulingEnabled() {
 #endif
 }
 
+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(cc::switches::kDisableStartCommitBeforeDraw))
+    return false;
+  else if (command_line.HasSwitch(cc::switches::kEnableStartCommitBeforeDraw))
+    return true;
+
+#if defined(OS_ANDROID)
+  return true;
+#else
+  return false;
+#endif
+}
+
+bool IsStartCommitBeforeActivateEnabled() {
+  const CommandLine& command_line = *CommandLine::ForCurrentProcess();
+
+  if (command_line.HasSwitch(cc::switches::kDisableStartCommitBeforeActivate))
+    return false;
+  else if (
+      command_line.HasSwitch(cc::switches::kEnableStartCommitBeforeActivate))
+    return true;
+
+#if defined(OS_ANDROID)
+  return true;
+#else
+  return false;
+#endif
+}
+
 }  // namespace switches
 }  // namespace cc