Add GL_ANGLE_pack_reverse_row_order to command buffer

gpu/command_buffer/client/gles2_implementation.cc

Index: gpu/command_buffer/client/gles2_implementation.cc
===================================================================
--- gpu/command_buffer/client/gles2_implementation.cc	(revision 110309)
+++ gpu/command_buffer/client/gles2_implementation.cc	(working copy)
@@ -543,6 +543,7 @@
       pack_alignment_(4),
       unpack_alignment_(4),
       unpack_flip_y_(false),
+      pack_flip_y_(false),
       active_texture_unit_(0),
       bound_framebuffer_(0),
       bound_renderbuffer_(0),
@@ -1221,6 +1222,9 @@
     case GL_UNPACK_FLIP_Y_CHROMIUM:
         unpack_flip_y_ = (param != 0);
         return;
+    case GL_PACK_FLIP_Y_ANGLE:
+        pack_flip_y_ = (param != 0);
+        break;
     default:
         break;
   }
@@ -1975,13 +1979,25 @@
           result_shm_id(), result_shm_offset());
       WaitForCmd();
       if (*result != 0) {
+        // when doing a y-flip we have to iterate through top-to-bottom chunks
+        // of the dst. The service side handles reversing the rows within a
+        // chunk.
+        int8* rows_dst;
+        if (pack_flip_y_) {
+            rows_dst = dest + (height - num_rows) * padded_row_size;
+        } else {
+            rows_dst = dest;
+        }
         // We have to copy 1 row at a time to avoid writing pad bytes.
         const int8* src = static_cast<const int8*>(buffer);
         for (GLint yy = 0; yy < num_rows; ++yy) {
-          memcpy(dest, src, unpadded_row_size);
-          dest += padded_row_size;
+          memcpy(rows_dst, src, unpadded_row_size);
+          rows_dst += padded_row_size;
           src += padded_row_size;
         }
+        if (!pack_flip_y_) {
+          dest = rows_dst;
+        }
       }
       transfer_buffer_.FreePendingToken(buffer, helper_->InsertToken());
       // If it was not marked as successful exit.
@@ -1998,6 +2014,10 @@
     GLsizeiptr element_size = temp_size;
     max_size -= max_size % element_size;
     GLint max_sub_row_pixels = max_size / element_size;
+    if (pack_flip_y_) {
+      // start at the last row when flipping y.
+      dest = dest + (height - 1) * padded_row_size;
+    }
     for (; height; --height) {
       GLint temp_width = width;
       GLint temp_xoffset = xoffset;
@@ -2025,7 +2045,7 @@
         temp_width -= num_pixels;
       }
       ++yoffset;
-      dest += padded_row_size;
+      dest += pack_flip_y_ ? -padded_row_size : padded_row_size;
     }
   }
 }