Reduce unintended scrolling by increasing touch slop tolerance

Vertical touch distance required to start scrolling is increased
from 0.165 to 0.185, and horizontal distance is increased from
0.15 to 0.17.

BUG=740001

Change-Id: I9ea9c16052e0ea490de7ecf92f164701554475a3
Reviewed-on: https://chromium-review.googlesource.com/811665Reviewed-by: Biao She <bshe@chromium.org>
Commit-Queue: Amirhossein Simjour <asimjour@chromium.org>
Cr-Commit-Position: refs/heads/master@{#522455}

chrome/browser/android/vr_shell/vr_controller.cc

@@ -28,10 +28,10 @@ constexpr float kDisplacementScaleFactor = 300.0f;
 // If the user does not move outside of the slop, no gesture is detected.
 // Gestures start to be detected when the user moves outside of the slop.
 // Vertical distance from the border to the center of slop.
-constexpr float kSlopVertical = 0.165f;
+constexpr float kSlopVertical = 0.185f;
 
 // Horizontal distance from the border to the center of slop.
-constexpr float kSlopHorizontal = 0.15f;
+constexpr float kSlopHorizontal = 0.17f;
 
 // Minimum distance needed in at least one direction to call two vectors
 // not equal. Also, minimum time distance needed to call two timestamps