Provide max gesture bounds and option to ignore touch size during pinch

ui/events/gesture_detection/gesture_config_helper_android.cc

Index: ui/events/gesture_detection/gesture_config_helper_android.cc
diff --git a/ui/events/gesture_detection/gesture_config_helper_android.cc b/ui/events/gesture_detection/gesture_config_helper_android.cc
index 546cb84e1193635965d49523fcc19fc4a1da1226..fbaba5771ea2529b6528f82f5421870c1414fea3 100644
--- a/ui/events/gesture_detection/gesture_config_helper_android.cc
+++ b/ui/events/gesture_detection/gesture_config_helper_android.cc
@@ -17,6 +17,10 @@ namespace {
 // detection pipeline.
 const float kMinGestureBoundsLengthDips = 24.f;
 
+// This value is somewhat arbitrary, but provides a reasonable maximum
+// approximating a large thumb depression.
+const float kMaxGestureBoundsLengthDips = kMinGestureBoundsLengthDips * 4.f;
+
 GestureDetector::Config DefaultGestureDetectorConfig(
     const gfx::Display& display) {
   GestureDetector::Config config;
@@ -51,8 +55,17 @@ ScaleGestureDetector::Config DefaultScaleGestureDetectorConfig(
   const float px_to_dp = 1.f / display.device_scale_factor();
   config.min_scaling_touch_major =
       ViewConfiguration::GetMinScalingTouchMajorInPixels() * px_to_dp;
+  config.use_touch_major_in_span =
+      ViewConfiguration::ShouldUseTouchMajorInScalingSpan();
   config.min_scaling_span =
       ViewConfiguration::GetMinScalingSpanInPixels() * px_to_dp;
+  // As the |min_scaling_span| platform constant assumes that touch major values
+  // are used when computing the span, subtract off a reasonable touch major
+  // value for the case where the touch major values are not used.
+  if (!config.use_touch_major_in_span) {
+    config.min_scaling_span = std::max(
+        0.f, config.min_scaling_span - 2.f * config.min_scaling_touch_major);
+  }
 
   return config;
 }
@@ -67,6 +80,7 @@ GestureProvider::Config DefaultGestureProviderConfig() {
       DefaultScaleGestureDetectorConfig(config.display);
   config.gesture_begin_end_types_enabled = false;
   config.min_gesture_bounds_length = kMinGestureBoundsLengthDips;
+  config.max_gesture_bounds_length = kMaxGestureBoundsLengthDips;
   return config;
 }