Remove unused ENABLE_ANDROID_INSTALLABLE_WEB_APPS

 Remove an unused #define and code associated with it. This will
 smooth a possible future webkit merge.
 WebKit change: I16d8c457a3f08996bc66401b241fe0db5a118975

Change-Id: Ibf046337cdabb9bee9cff8e3d77d9f69a59ecb15
3 files changed