gpu: Make pack/unpack alignment part of autogenerated state

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 9bc5823a1b9311ffd3917da1cfdff543f8ed3ac8..9b7601dae7b40e077fefae0c656c97bc708fae9c 100755
--- a/gpu/command_buffer/build_gles2_cmd_buffer.py
+++ b/gpu/command_buffer/build_gles2_cmd_buffer.py
@@ -361,10 +361,26 @@ _STATES = {
       }
     ],
   },
+  'PixelStore': {
+    'type': 'NamedParameter',
+    'func': 'PixelStorei',
+    'states': [
+      {
+        'name': 'pack_alignment',
+        'type': 'GLint',
+        'enum': 'GL_PACK_ALIGNMENT',
+        'default': '4'
+      },
+      {
+        'name': 'unpack_alignment',
+        'type': 'GLint',
+        'enum': 'GL_UNPACK_ALIGNMENT',
+        'default': '4'
+      }
+    ],
+  },
   # TODO: Consider implemenenting these states
-  # GL_ACTIVE_TEXTURE,
-  # GL_PACK_ALIGNMENT,
-  # GL_UNPACK_ALIGNMENT
+  # GL_ACTIVE_TEXTURE
   'LineWidth': {
     'type': 'Normal',
     'func': 'LineWidth',