Add experimental geometry shader code to gpu backend

Review URL: http://codereview.appspot.com/5129047/


git-svn-id: http://skia.googlecode.com/svn/trunk@2365 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gpu/include/GrGLDefines.h b/gpu/include/GrGLDefines.h
index 73c2a71..dcacb77 100644
--- a/gpu/include/GrGLDefines.h
+++ b/gpu/include/GrGLDefines.h
@@ -299,6 +299,7 @@
 /* Shaders */
 #define GR_GL_FRAGMENT_SHADER                  0x8B30
 #define GR_GL_VERTEX_SHADER                    0x8B31
+#define GR_GL_GEOMETRY_SHADER                  0x8DD9
 #define GR_GL_MAX_VERTEX_ATTRIBS               0x8869
 #define GR_GL_MAX_VERTEX_UNIFORM_VECTORS       0x8DFB
 #define GR_GL_MAX_VARYING_VECTORS              0x8DFC