[TTS] Basic Tap Suppression functionality.

chrome/android/java/src/org/chromium/chrome/browser/contextualsearch/TapSuppression.java

Index: chrome/android/java/src/org/chromium/chrome/browser/contextualsearch/TapSuppression.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/contextualsearch/TapSuppression.java b/chrome/android/java/src/org/chromium/chrome/browser/contextualsearch/TapSuppression.java
new file mode 100644
index 0000000000000000000000000000000000000000..07d6558c773ea3761c6982a979fbefb5f0be76f0
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/contextualsearch/TapSuppression.java
@@ -0,0 +1,95 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.chrome.browser.contextualsearch;
+
+/**
+ * Heuristic for general Tap suppression that factors in a variety of signals.
+ */
+class TapSuppression extends ContextualSearchHeuristic {
+    private static final int TIME_THRESHOLD_MILLISECONDS = 3000;
+    private static final int TAP_RADIUS_DPS = 30;
+
+    private final boolean mIsTapSuppressionEnabled;
+    private final int mExperimentThresholdTaps;
+    private final int mTapsSinceOpen;
+    private final float mPxToDp;
+    private final boolean mIsSecondTap;
+    private final boolean mIsConditionSatisfied; // whether to suppress or not.
+
+    /**
+     * Constructs a heuristic to decide if a Tap should be suppressed or not.
+     * Combines various signals to determine suppression, including whether the previous
+     * Tap was suppressed for any reason.
+     * @param controller The Selection Controller.
+     * @param previousTapState The specifics regarding the previous Tap.
+     * @param x The x coordinate of the current tap.
+     * @param y The y coordinate of the current tap.
+     * @param tapsSinceOpen the number of Tap gestures since the last open of the panel.
+     */
+    TapSuppression(ContextualSearchSelectionController controller,
+            ContextualSearchTapState previousTapState, int x, int y, int tapsSinceOpen) {
+        mIsTapSuppressionEnabled = ContextualSearchFieldTrial.isTapSuppressionEnabled();
+        mExperimentThresholdTaps = ContextualSearchFieldTrial.getSuppressionTaps();
+        mPxToDp = controller.getPxToDp();
+        mTapsSinceOpen = tapsSinceOpen;
+        mIsSecondTap = previousTapState != null && previousTapState.wasSuppressed()

[Theresa, 2016/06/29 01:51:57]

Could the previous tap have been suppressed for a reason other than our tap
suppression threshold? Do we care?

[Donn Denman, 2016/06/29 02:30:36]

Yes, it could have for TapFarFromPreviousSuppression, but we don't care, as long
as shouldHandleFirstTap returns true we can safely consider this a second tap.

+                && !shouldHandleFirstTap();
+
+        boolean doSuppressTap = false;
+        if (mIsTapSuppressionEnabled) {
+            if (mIsSecondTap) {
+                boolean shouldHandle = shouldHandleSecondTap(previousTapState, x, y);
+                doSuppressTap = !shouldHandle;

[Theresa, 2016/06/29 01:51:57]

nit: combine with line above?

[Donn Denman, 2016/06/29 02:30:36]

Done.

+            } else {
+                doSuppressTap = !shouldHandleFirstTap();
+            }
+        }
+        mIsConditionSatisfied = doSuppressTap;
+    }
+
+    @Override
+    protected boolean isConditionSatisfied() {
+        return mIsConditionSatisfied;
+    }
+
+    @Override
+    protected void logResultsSeen(boolean wasSearchContentViewSeen, boolean wasActivatedByTap) {
+        // TODO(donnd): consider logging counter-factual data rather than checking if enabled.
+        if (wasActivatedByTap && mIsTapSuppressionEnabled) {
+            ContextualSearchUma.logTapSuppressionResultsSeen(
+                    wasSearchContentViewSeen, mIsSecondTap);
+        }
+    }
+
+    /**
+     * @return whether a first tap should be handled or not.
+     */
+    private boolean shouldHandleFirstTap() {
+        return mTapsSinceOpen < mExperimentThresholdTaps;
+    }
+
+    /**
+     * Determines whether a second tap at the given coordinates should be handled.
+     * @param tapState The specifics regarding the previous Tap.
+     * @param x The x coordinate of the current tap.
+     * @param y The y coordinate of the current tap.
+     * @return whether a second tap at the given coordinates should be handled or not.
+     */
+    private boolean shouldHandleSecondTap(ContextualSearchTapState tapState, int x, int y) {
+        // The second tap needs to be close to the first tap in both time and space.
+        // Recent enough?
+        if (System.nanoTime() - tapState.tapTimeNanoseconds()
+                > (long) TIME_THRESHOLD_MILLISECONDS * NANOSECONDS_IN_A_MILLISECOND) {
+            return false;
+        }
+
+        // Within our radius?
+        float deltaXDp = (tapState.getX() - x) * mPxToDp;
+        float deltaYDp = (tapState.getY() - y) * mPxToDp;
+        // Use x^2 * y^2 = r^2
+        float distanceSquaredDp = deltaXDp * deltaXDp + deltaYDp * deltaYDp;
+        return distanceSquaredDp <= TAP_RADIUS_DPS * TAP_RADIUS_DPS;
+    }
+}