Add support for glMapBufferRange. Use glMapBufferRange and glMapBufferSubData.

include/gpu/gl/GrGLFunctions.h

Index: include/gpu/gl/GrGLFunctions.h
diff --git a/include/gpu/gl/GrGLFunctions.h b/include/gpu/gl/GrGLFunctions.h
index 3f8736555ab6a2d79d3324885ac162d36ee56965..51db053276c41f426ed0f8a110e2ecdf5d08f027 100644
--- a/include/gpu/gl/GrGLFunctions.h
+++ b/include/gpu/gl/GrGLFunctions.h
@@ -111,6 +111,7 @@ extern "C" {
     typedef GrGLvoid (GR_GL_FUNCTION_TYPE* GrGLEndQueryProc)(GrGLenum target);
     typedef GrGLvoid (GR_GL_FUNCTION_TYPE* GrGLFinishProc)();
     typedef GrGLvoid (GR_GL_FUNCTION_TYPE* GrGLFlushProc)();
+    typedef GrGLvoid (GR_GL_FUNCTION_TYPE* GrGLFlushMappedBufferRangeProc)(GrGLenum target, GrGLintptr offset, GrGLsizeiptr length);
     typedef GrGLvoid (GR_GL_FUNCTION_TYPE* GrGLFramebufferRenderbufferProc)(GrGLenum target, GrGLenum attachment, GrGLenum renderbuffertarget, GrGLuint renderbuffer);
     typedef GrGLvoid (GR_GL_FUNCTION_TYPE* GrGLFramebufferTexture2DProc)(GrGLenum target, GrGLenum attachment, GrGLenum textarget, GrGLuint texture, GrGLint level);
     typedef GrGLvoid (GR_GL_FUNCTION_TYPE* GrGLFramebufferTexture2DMultisampleProc)(GrGLenum target, GrGLenum attachment, GrGLenum textarget, GrGLuint texture, GrGLint level, GrGLsizei samples);
@@ -150,6 +151,7 @@ extern "C" {
     typedef GrGLvoid (GR_GL_FUNCTION_TYPE* GrGLLineWidthProc)(GrGLfloat width);
     typedef GrGLvoid (GR_GL_FUNCTION_TYPE* GrGLLinkProgramProc)(GrGLuint program);
     typedef GrGLvoid* (GR_GL_FUNCTION_TYPE* GrGLMapBufferProc)(GrGLenum target, GrGLenum access);
+    typedef GrGLvoid* (GR_GL_FUNCTION_TYPE* GrGLMapBufferRangeProc)(GrGLenum target, GrGLintptr offset, GrGLsizeiptr length, GrGLbitfield access);
     typedef GrGLvoid* (GR_GL_FUNCTION_TYPE* GrGLMapBufferSubDataProc)(GrGLuint target, GrGLintptr offset, GrGLsizeiptr size, GrGLenum access);
     typedef GrGLvoid* (GR_GL_FUNCTION_TYPE* GrGLMapTexSubImage2DProc)(GrGLenum target, GrGLint level, GrGLint xoffset, GrGLint yoffset, GrGLsizei width, GrGLsizei height, GrGLenum format, GrGLenum type, GrGLenum access);
     typedef GrGLvoid (GR_GL_FUNCTION_TYPE* GrGLPixelStoreiProc)(GrGLenum pname, GrGLint param);