[TTS] Add some initial signals for Tap in content.

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

Index: chrome/android/java/src/org/chromium/chrome/browser/contextualsearch/TapWordEdgeSuppression.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/contextualsearch/TapWordEdgeSuppression.java b/chrome/android/java/src/org/chromium/chrome/browser/contextualsearch/TapWordEdgeSuppression.java
new file mode 100644
index 0000000000000000000000000000000000000000..0e25b12e9825860d3b1924899495aac053c04df4
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/contextualsearch/TapWordEdgeSuppression.java
@@ -0,0 +1,75 @@
+// Copyright 2017 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;
+
+import android.text.TextUtils;
+
+/**
+ * Implements the policy that a Tap relatively far away from the middle of a word should be
+ * ignored.  When a Tap is close to the middle of the word tapped it's treated normally.
+ */
+class TapWordEdgeSuppression extends ContextualSearchHeuristic {
+    private static final int INVALID_OFFSET = ContextualSearchContext.INVALID_OFFSET;
+    private static final int MIN_WORD_LENGTH = 4;
+    private static final double MIN_WORD_START_RATIO = 0.25;
+    private static final double MIN_WORD_END_RATIO = 0.25;
+
+    private final boolean mIsSuppressionEnabled;
+    private final boolean mIsConditionSatisfied;
+
+    /**
+     * Constructs a heuristic to determine if the current Tap is close to the edge of the word.
+     * @param contextualSearchContext The current {@link ContextualSearchContext} so we can figure
+     *        out what part of the word has been tapped.
+     */
+    TapWordEdgeSuppression(ContextualSearchContext contextualSearchContext) {
+        mIsSuppressionEnabled = ContextualSearchFieldTrial.isWordEdgeSuppressionEnabled();
+        mIsConditionSatisfied = isTapNearWordEdge(contextualSearchContext);
+    }
+
+    @Override
+    protected boolean isConditionSatisfiedAndEnabled() {
+        return mIsSuppressionEnabled && mIsConditionSatisfied;
+    }
+
+    @Override
+    protected void logResultsSeen(boolean wasSearchContentViewSeen, boolean wasActivatedByTap) {
+        if (wasActivatedByTap) {
+            ContextualSearchUma.logTapOnWordMiddleSeen(
+                    wasSearchContentViewSeen, !mIsConditionSatisfied);
+        }
+    }
+
+    @Override
+    protected boolean shouldAggregateLogForTapSuppression() {
+        return true;
+    }
+
+    @Override
+    protected boolean isConditionSatisfiedForAggregateLogging() {
+        return mIsConditionSatisfied;
+    }
+
+    /**
+     * Whether the tap is near the word edge and not a second-tap (tap following a suppressed tap).
+     * @param contextualSearchContext The {@link ContextualSearchContext}, used to determine how
+     *        close the tap offset is to the word edges.
+     * @return Whether the tap is near an edge and not a second tap.
+     */
+    private boolean isTapNearWordEdge(ContextualSearchContext contextualSearchContext) {
+        // If setup failed, don't suppress.
+        String tappedWord = contextualSearchContext.getTappedWord();
+        int tapOffset = contextualSearchContext.getTappedWordOffset();
+        if (TextUtils.isEmpty(tappedWord) || tapOffset == INVALID_OFFSET) return false;
+
+        // If the word is long enough, suppress if the tap was near one end or the other.
+        boolean isInStartEdge = (double) tapOffset / tappedWord.length() < MIN_WORD_START_RATIO;
+        boolean isInEndEdge = (double) (tappedWord.length() - tapOffset) / tappedWord.length()
+                < MIN_WORD_END_RATIO;
+        if (tappedWord.length() >= MIN_WORD_LENGTH && (isInStartEdge || isInEndEdge)) return true;
+
+        return false;
+    }
+}