Update: the case when no color conversion is needed still needs to copy the data as the call site (BaseRenderingContext2D::putImageData) wants to consume the data by putting it in an ImageBuffer.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/48eb6e065cce65ff57d7eb1c193f4b50ef34c5b8

commit 48eb6e065cce65ff57d7eb1c193f4b50ef34c5b8
Author: Reza.Zakerinasab <zakerinasab@chromium.org>
Date: Tue Sep 19 03:02:42 2017

Avoid data copy in ImageData for BE<->LE conversions

ImageData::ImageDataInCanvasColorSettings() creates an extra copy of data when image data uses U16 storage format and data must get converted from Little Endian to Big Endian. This change refactors this function to remove this extra copy.

Bug:  766018 
Change-Id: I54b90f79887be884449d0d4739c990e21bc6aa5b
Reviewed-on: https://chromium-review.googlesource.com/670520
Reviewed-by: Xida Chen <xidachen@chromium.org>
Reviewed-by: Justin Novosad <junov@chromium.org>
Commit-Queue: Mohammad Reza Zakerinasab <zakerinasab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#502768}
[modify] https://crrev.com/48eb6e065cce65ff57d7eb1c193f4b50ef34c5b8/third_party/WebKit/Source/core/html/ImageData.cpp