Change desktop and ES 3.0 to always use sized internal texture formats.

Committed: https://skia.googlesource.com/skia/+/bc02bf0ee4221604796cd6d0394ca3af60c0a579

Review URL: https://codereview.chromium.org/806943002
diff --git a/src/gpu/gl/GrGLDefines.h b/src/gpu/gl/GrGLDefines.h
index dc9468f..0eb5149 100644
--- a/src/gpu/gl/GrGLDefines.h
+++ b/src/gpu/gl/GrGLDefines.h
@@ -736,6 +736,7 @@
 #define GR_GL_RGB565                         0x8D62
 #define GR_GL_RGBA8                          0x8058
 #define GR_GL_RGBA32F                        0x8814
+#define GR_GL_RGB5                           0x8050
 #define GR_GL_RGB8                           0x8051
 #define GR_GL_BGRA8                          0x93A1
 #define GR_GL_SRGB                           0x8C40