Expose DXT3 and DXT5 through ANGLE

gpu/GLES2/gl2ext.h

Index: gpu/GLES2/gl2ext.h
diff --git a/gpu/GLES2/gl2ext.h b/gpu/GLES2/gl2ext.h
index c2bec346a0669d99733d4d41a331e1fe22b3d35e..68773a41ae46e62ef251155ab43d8016e3dd2cd7 100644
--- a/gpu/GLES2/gl2ext.h
+++ b/gpu/GLES2/gl2ext.h
@@ -1034,6 +1034,18 @@ typedef void (GL_APIENTRYP PFNGLGETPROGRAMINFOCHROMIUM) ();
 #define GL_UNPACK_FLIP_Y_CHROMIUM 0x9240
 #endif
 
+/* GL_CHROMIUM_texture_compression_dxt3 */
+#ifndef GL_CHROMIUM_texture_compression_dxt3
+#define GL_CHROMIUM_texture_compression_dxt3 1
+#define GL_COMPRESSED_RGBA_S3TC_DXT3_EXT  0x83F2
+#endif
+
+/* GL_CHROMIUM_texture_compression_dxt5 */
+#ifndef GL_CHROMIUM_texture_compression_dxt5
+#define GL_CHROMIUM_texture_compression_dxt5 1
+#define GL_COMPRESSED_RGBA_S3TC_DXT5_EXT  0x83F3
+#endif
+
 /* GL_ARB_robustness */
 /* This extension is subsetted for the moment, incorporating only the
  * enums necessary to describe the reasons that we might encounter for