Make ANGLE perf decisions be runtime rather than compile time

src/gpu/gl/GrGLUtil.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrGLUtil_DEFINED
 #define GrGLUtil_DEFINED
 
@@ skipping 41 matching lines @@
     kAdreno3xx_GrGLRenderer,
     kAdreno4xx_GrGLRenderer,
     kOther_GrGLRenderer
 };
 
 enum GrGLDriver {
     kMesa_GrGLDriver,
     kChromium_GrGLDriver,
     kNVIDIA_GrGLDriver,
     kIntel_GrGLDriver,
+    kANGLE_GrGLDriver,
     kUnknown_GrGLDriver
 };
 
 ////////////////////////////////////////////////////////////////////////////////
 
 /**
  *  Some drivers want the var-int arg to be zero-initialized on input.
  */
 #define GR_GL_INIT_ZERO     0
 #define GR_GL_GetIntegerv(gl, e, p)                                            \
@@ skipping 136 matching lines @@
         GR_GL_LOG_CALLS_IMPL(X);                                \
     } while (false)
 
 // call glGetError without doing a redundant error check or logging.
 #define GR_GL_GET_ERROR(IFACE) (IFACE)->fFunctions.fGetError()
 
 GrGLenum GrToGLStencilFunc(GrStencilFunc basicFunc);
 
 
 #endif