Don't dispatch a 'click' event for mousedown/mouseup across form controls.

LayoutTests/fast/dom/shadow/select-in-shadowdom.html

Index: LayoutTests/fast/dom/shadow/select-in-shadowdom.html
diff --git a/LayoutTests/fast/dom/shadow/select-in-shadowdom.html b/LayoutTests/fast/dom/shadow/select-in-shadowdom.html
index abefb0f3bd454096d95334af050cb89d69dcf785..b0d747061d10255c8b2b94c48b1906a7582c73ef 100644
--- a/LayoutTests/fast/dom/shadow/select-in-shadowdom.html
+++ b/LayoutTests/fast/dom/shadow/select-in-shadowdom.html
@@ -26,12 +26,12 @@ shadowRoot.lastChild.addEventListener('click', function(e) {
     testFailed('Click event on an anchor element should not be fired.');
 }, false);
 
-debug('Selecting from a node to another node in ShadowDOM. This should fire click event on the host.');
+debug('Selecting from a node to another node in ShadowDOM. This should not start page navigation.');
 mouseMoveTo(shadowRoot.firstChild);
 eventSender.mouseDown();
 mouseMoveTo(shadowRoot.firstChild.nextSibling);
 eventSender.mouseUp();
-shouldBe('lastClickTarget', 'host');
+shouldBeNull('lastClickTarget');
 debug('');
 
 lastClickTarget = null;