Change pointer id to differentiate from other pointer type

In WebDriver spec, we assume that the actions with the same id and type
are the same, we should give the pointer actions of different source
types a different id.

Bug: 606367
Change-Id: I1d8f6a08ee8d98c4afd281f077e23067ad915ec3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1626960Reviewed-by: Navid Zolghadr <nzolghadr@chromium.org>
Commit-Queue: Lan Wei <lanwei@chromium.org>
Cr-Commit-Position: refs/heads/master@{#663758}

third_party/blink/web_tests/external/wpt/pointerevents/pointerevent_pointerout_pen.html

@@ -51,7 +51,7 @@
 
                 // Inject pen inputs.
                 new test_driver.Actions()
-                  .addPointer("pointer1", "pen")
+                  .addPointer("PenPointer1", "pen")
                   .pointerMove(0, 0, {origin: target0})
                   .pointerMove(0, 0)
                   .send();