API for ImageDecoder to support downsampling

Adding a new ImageDecoder::setMaxDecodedSize() API. The purpose of this
API is to restrict the size of output by the decoder. This is used for
low end devices where memory is limited.

This API is optionally supported by each image format. Decoder can
choose a size that fits into the specified limit.

Using this API the image will report the same size such that page layout
would not change but the bitmap decoded will be smaller.

Implemented for JPEG is included in this change.

BUG=276666

Review URL: https://chromiumcodereview.appspot.com/23455022

git-svn-id: svn://svn.chromium.org/blink/trunk@157336 bbb929c8-8fbe-4397-9dbb-9b2b20218538