Send early ShowPress on TapDown when page isn't scrollable/pinchable.

LayoutTests/fast/events/touch/gesture/gesture-tap-down-special-elements-expected.txt

+        
+Tests gesture tapdown behaviour on different form elements.
+
+On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
+
+
+See http://crbug.com/316974 for details
+
+PASS successfullyParsed is true
+
+TEST COMPLETE
+Scroll and Pinch are disabled on the page
+Verify hover, active aren't initially set
+PASS isBoxDefault('combobox') is true
+combobox should always be activated on tapdown
+PASS isBoxHoverActive('combobox') is true
+Verify hover, active aren't initially set
+PASS isBoxDefault('listbox') is true
+Overflow listbox should remain unchanged
+PASS isBoxDefault('listbox') is true
+Verify hover, active aren't initially set
+PASS isBoxDefault('textbox') is true
+Overflow textbox should remain unchanged
+PASS isBoxDefault('textbox') is true
+Verify hover, active aren't initially set
+PASS isBoxDefault('textarea') is true
+Overflow textarea should remain unchanged
+PASS isBoxDefault('textarea') is true
+Verify hover, active aren't initially set
+PASS isFrameDefault() is true
+Overflow iframe should remain unchanged
+PASS isFrameDefault() is true
+