Add support for half float alpha textures.

src/gpu/gl/GrGLDefines.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 
 #ifndef GrGLDefines_DEFINED
@@ skipping 284 matching lines @@
 #define GR_GL_GENERATE_MIPMAP_HINT            0x8192
 
 /* DataType */
 #define GR_GL_BYTE                           0x1400
 #define GR_GL_UNSIGNED_BYTE                  0x1401
 #define GR_GL_SHORT                          0x1402
 #define GR_GL_UNSIGNED_SHORT                 0x1403
 #define GR_GL_INT                            0x1404
 #define GR_GL_UNSIGNED_INT                   0x1405
 #define GR_GL_FLOAT                          0x1406
+#define GR_GL_HALF_FLOAT                     0x140B
 #define GR_GL_FIXED                          0x140C
+#define GR_GL_HALF_FLOAT_OES                 0x8D61
 
 /* Lighting */
 #define GR_GL_LIGHTING                       0x0B50
 #define GR_GL_LIGHT0                         0x4000
 #define GR_GL_LIGHT1                         0x4001
 #define GR_GL_LIGHT2                         0x4002
 #define GR_GL_LIGHT3                         0x4003
 #define GR_GL_LIGHT4                         0x4004
 #define GR_GL_LIGHT5                         0x4005
 #define GR_GL_LIGHT6                         0x4006
@@ skipping 56 matching lines @@
 #define GR_GL_ALPHA                          0x1906
 #define GR_GL_RGB                            0x1907
 #define GR_GL_RGBA                           0x1908
 #define GR_GL_BGRA                           0x80E1
 #define GR_GL_LUMINANCE                      0x1909
 #define GR_GL_LUMINANCE_ALPHA                0x190A
 #define GR_GL_PALETTE8_RGBA8                 0x8B96
 #define GR_GL_ALPHA8                         0x803C
 
 #define GR_GL_R8                             0x8229
+#define GR_GL_R16F                           0x822D
+#define GR_GL_ALPHA16F                       0x881C
 
 /* PixelType */
 /*      GL_UNSIGNED_BYTE */
 #define GR_GL_UNSIGNED_SHORT_4_4_4_4         0x8033
 #define GR_GL_UNSIGNED_SHORT_5_5_5_1         0x8034
 #define GR_GL_UNSIGNED_SHORT_5_6_5           0x8363
 
 /* Shaders */
 #define GR_GL_FRAGMENT_SHADER                  0x8B30
 #define GR_GL_VERTEX_SHADER                    0x8B31
@@ skipping 451 matching lines @@
 // NV_path_rendering extension to EXT_direct_state_access:
 // [the matrix functions] must support the PATH_PROJECTION_NV and
 // PATH_MODELVIEW_NV tokens for matrixMode.
 #define GR_GL_PATH_PROJECTION                               0x1701
 #define GR_GL_PATH_MODELVIEW                                0x1700
 
 /*  ARM specific define for MSAA support on framebuffer fetch */
 #define GR_GL_FETCH_PER_SAMPLE_ARM                          0x8F65
 
 #endif