content: Implement dynamic priorities for raster threads.

base/threading/platform_thread.h

Index: base/threading/platform_thread.h
diff --git a/base/threading/platform_thread.h b/base/threading/platform_thread.h
index e62eb2b2c18475adeeb902f6b248e023dae69b2c..90074e201947ef52a432f7de9a8e638263ab6c34 100644
--- a/base/threading/platform_thread.h
+++ b/base/threading/platform_thread.h
@@ -191,6 +191,13 @@ class BASE_EXPORT PlatformThread {
 
   static ThreadPriority GetCurrentThreadPriority();
 
+  // Sets priority of child thread in current process. If called from other
+  // process, this function has no effect. If successful, returns true.
+  static bool SetChildThreadPriorityInCurrentProcess(
+      PlatformThreadHandle thread_handle,
+      PlatformThreadId tid,
+      ThreadPriority priority);
+
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PlatformThread);
 };