Revert of Make the Sk GL context class an abstract base class

tools/timer/Timer.h

Index: tools/timer/Timer.h
diff --git a/tools/timer/Timer.h b/tools/timer/Timer.h
index 81d1ca50ef8922495c6c732a3e912bb045454c9e..15c93f5603cae9478574a7136069a163ca427768 100644
--- a/tools/timer/Timer.h
+++ b/tools/timer/Timer.h
@@ -21,7 +21,7 @@
     #include "GpuTimer.h"
 #endif
 
-class SkGLContext;
+class SkGLContextHelper;
 
 /**
  * SysTimers and GpuTimers are implemented orthogonally.
@@ -34,7 +34,7 @@
  */
 class Timer {
 public:
-    explicit Timer(SkGLContext* gl = NULL);
+    explicit Timer(SkGLContextHelper* gl = NULL);
 
     void start();
     void truncatedEnd();