Changes to make the cursor blink at the correct times.

Make the blinking caret active when the user actually starts editing
text.  To be consistent with that idea, do not rebuild the WebTextView
when the WebView regains focus.  Now sendMouseMoveIfLatest takes a
boolean parameter to determine whether to make the focusController
inactive.  Requires a matching change in webkit to pass a parameter
to the method.  Now that we only call setFocusControllerActive with
false, change the method to no longer take a boolean parameter.
Change names to reflect that.

This change also reflects a behavioral change.  If the WebView or
its window lose focus, we do not restore the blinking caret when
focus returns.