Experimental feature: use WebKit to find out the selection
highlight.

The new setting, supportTouchOnly(), is currently not
fully implemented. It is overloaded with mLightTouchEnabled
for short term testing. To test the feature, please
use the "Enable Light Touch" in the debug settings.

When supportTouchOnly is true, we are not using nav
cache to display the yellow ring. Instead we show 
the gray rectangle(s) based on the calculation from
WebKit. When short press happens, we current use 0
for mMoveGeneration so that it will trigger WebKit
to use the same point when it calculates the highlight.

If you turn on NavDump in the debug settings, it will
also draw the fat point where you tap on the screen.

Known issues, it is not fully synced with IME. If you
tap a text input box also in focus, the yellow ring
will show up. If you leave the text input field, the
IME is not dismissed. If this passes the user tests,
we will make a special mode and fix all these issues.

There is another matching CL in external/webkit
3 files changed