Get ReadPixels to work with INT and UNSIGNED_INT format.

gpu/command_buffer/build_gles2_cmd_buffer.py

Index: gpu/command_buffer/build_gles2_cmd_buffer.py
diff --git a/gpu/command_buffer/build_gles2_cmd_buffer.py b/gpu/command_buffer/build_gles2_cmd_buffer.py
index 79629552293414ee17f0cda2f0fc68584e05609b..30a9a1a27e83b4621ee87e72d92920909fb72714 100755
--- a/gpu/command_buffer/build_gles2_cmd_buffer.py
+++ b/gpu/command_buffer/build_gles2_cmd_buffer.py
@@ -2230,12 +2230,14 @@ _FUNCTION_INFO = {
     'type': 'PUT',
     'use_count_func': True,
     'count': 4,
+    'decoder_func': 'DoClearBufferiv',
     'unsafe': True,
     'trace_level': 2,
   },
   'ClearBufferuiv': {
     'type': 'PUT',
     'count': 4,
+    'decoder_func': 'DoClearBufferuiv',
     'unsafe': True,
     'trace_level': 2,
   },
@@ -2243,11 +2245,13 @@ _FUNCTION_INFO = {
     'type': 'PUT',
     'use_count_func': True,
     'count': 4,
+    'decoder_func': 'DoClearBufferfv',
     'unsafe': True,
     'trace_level': 2,
   },
   'ClearBufferfi': {
     'unsafe': True,
+    'decoder_func': 'DoClearBufferfi',
     'trace_level': 2,
   },
   'ClearColor': {