Revert of Fix to remove customised String over IPC for SmartClip (https://codereview.chromium.org/259263003/)

Reason for revert:
android build was broken by this patch
http://build.chromium.org/p/chromium.webkit/builders/Android%20Builder/builds/39026/steps/compile/logs/stdio

Original issue's description:
> Fix to remove customised String over IPC for SmartClip
> 
> Currently, the data for SmartClip is sent over IPC as a customized
> string, which contains rect values and string of content within the
> clip rect. Changes from Blink side to remove custom serialization and
> send it as a structure of rect and string values.
> 
> BUG=330872
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=173295

TBR=eseidel@chromium.org,juhui24.lee@samsung.com,abarth@chromium.org,jam@chromium.org,jschuh@chromium.org,ch.dumez@samsung.com,avi.nitk@samsung.com
NOTREECHECKS=true
NOTRY=true
BUG=330872

Review URL: https://codereview.chromium.org/266193003

git-svn-id: svn://svn.chromium.org/blink/trunk@173296 bbb929c8-8fbe-4397-9dbb-9b2b20218538