diff --git a/java/src/com/android/inputmethod/keyboard/internal/GesturePreviewTrail.java b/java/src/com/android/inputmethod/keyboard/internal/GesturePreviewTrail.java
index e3e6d39..f682b51 100644
--- a/java/src/com/android/inputmethod/keyboard/internal/GesturePreviewTrail.java
+++ b/java/src/com/android/inputmethod/keyboard/internal/GesturePreviewTrail.java
@@ -37,6 +37,7 @@
 final class GesturePreviewTrail {
     private static final int DEFAULT_CAPACITY = GestureStrokeWithPreviewPoints.PREVIEW_CAPACITY;
 
+    // These three {@link ResizableIntArray}s should be synchronized by {@link #mEventTimes}.
     private final ResizableIntArray mXCoordinates = new ResizableIntArray(DEFAULT_CAPACITY);
     private final ResizableIntArray mYCoordinates = new ResizableIntArray(DEFAULT_CAPACITY);
     private final ResizableIntArray mEventTimes = new ResizableIntArray(DEFAULT_CAPACITY);
@@ -90,7 +91,13 @@
     }
 
     public void addStroke(final GestureStrokeWithPreviewPoints stroke, final long downTime) {
-        final int trailSize = mEventTimes.getLength();
+        synchronized (mEventTimes) {
+            addStrokeLocked(stroke, downTime);
+        }
+    }
+
+    private void addStrokeLocked(final GestureStrokeWithPreviewPoints stroke, final long downTime) {
+            final int trailSize = mEventTimes.getLength();
         stroke.appendPreviewStroke(mEventTimes, mXCoordinates, mYCoordinates);
         if (mEventTimes.getLength() == trailSize) {
             return;
@@ -169,6 +176,13 @@
      */
     public boolean drawGestureTrail(final Canvas canvas, final Paint paint,
             final Rect outBoundsRect, final Params params) {
+        synchronized (mEventTimes) {
+            return drawGestureTrailLocked(canvas, paint, outBoundsRect, params);
+        }
+    }
+
+    private boolean drawGestureTrailLocked(final Canvas canvas, final Paint paint,
+            final Rect outBoundsRect, final Params params) {
         // Initialize bounds rectangle.
         outBoundsRect.setEmpty();
         final int trailSize = mEventTimes.getLength();
diff --git a/java/src/com/android/inputmethod/latin/LatinIME.java b/java/src/com/android/inputmethod/latin/LatinIME.java
index 56b1c78..ec1816e 100644
--- a/java/src/com/android/inputmethod/latin/LatinIME.java
+++ b/java/src/com/android/inputmethod/latin/LatinIME.java
@@ -1551,7 +1551,8 @@
     private static final class BatchInputUpdater implements Handler.Callback {
         private final Handler mHandler;
         private LatinIME mLatinIme;
-        private boolean mInBatchInput; // synchronized using "this".
+        private final Object mLock = new Object();
+        private boolean mInBatchInput; // synchronized using {@link #mLock}.
 
         private BatchInputUpdater() {
             final HandlerThread handlerThread = new HandlerThread(
@@ -1582,21 +1583,25 @@
         }
 
         // Run in the UI thread.
-        public synchronized void onStartBatchInput(final LatinIME latinIme) {
-            mHandler.removeMessages(MSG_UPDATE_GESTURE_PREVIEW_AND_SUGGESTION_STRIP);
-            mLatinIme = latinIme;
-            mInBatchInput = true;
+        public void onStartBatchInput(final LatinIME latinIme) {
+            synchronized (mLock) {
+                mHandler.removeMessages(MSG_UPDATE_GESTURE_PREVIEW_AND_SUGGESTION_STRIP);
+                mLatinIme = latinIme;
+                mInBatchInput = true;
+            }
         }
 
         // Run in the Handler thread.
-        private synchronized void updateBatchInput(final InputPointers batchPointers) {
-            if (!mInBatchInput) {
-                // Batch input has ended or canceled while the message was being delivered.
-                return;
+        private void updateBatchInput(final InputPointers batchPointers) {
+            synchronized (mLock) {
+                if (!mInBatchInput) {
+                    // Batch input has ended or canceled while the message was being delivered.
+                    return;
+                }
+                final SuggestedWords suggestedWords = getSuggestedWordsGestureLocked(batchPointers);
+                mLatinIme.mHandler.showGesturePreviewAndSuggestionStrip(
+                        suggestedWords, false /* dismissGestureFloatingPreviewText */);
             }
-            final SuggestedWords suggestedWords = getSuggestedWordsGestureLocked(batchPointers);
-            mLatinIme.mHandler.showGesturePreviewAndSuggestionStrip(
-                    suggestedWords, false /* dismissGestureFloatingPreviewText */);
         }
 
         // Run in the UI thread.
@@ -1609,19 +1614,23 @@
                     .sendToTarget();
         }
 
-        public synchronized void onCancelBatchInput() {
-            mInBatchInput = false;
-            mLatinIme.mHandler.showGesturePreviewAndSuggestionStrip(
-                    SuggestedWords.EMPTY, true /* dismissGestureFloatingPreviewText */);
+        public void onCancelBatchInput() {
+            synchronized (mLock) {
+                mInBatchInput = false;
+                mLatinIme.mHandler.showGesturePreviewAndSuggestionStrip(
+                        SuggestedWords.EMPTY, true /* dismissGestureFloatingPreviewText */);
+            }
         }
 
         // Run in the UI thread.
-        public synchronized SuggestedWords onEndBatchInput(final InputPointers batchPointers) {
-            mInBatchInput = false;
-            final SuggestedWords suggestedWords = getSuggestedWordsGestureLocked(batchPointers);
-            mLatinIme.mHandler.showGesturePreviewAndSuggestionStrip(
-                    suggestedWords, true /* dismissGestureFloatingPreviewText */);
-            return suggestedWords;
+        public SuggestedWords onEndBatchInput(final InputPointers batchPointers) {
+            synchronized (mLock) {
+                mInBatchInput = false;
+                final SuggestedWords suggestedWords = getSuggestedWordsGestureLocked(batchPointers);
+                mLatinIme.mHandler.showGesturePreviewAndSuggestionStrip(
+                        suggestedWords, true /* dismissGestureFloatingPreviewText */);
+                return suggestedWords;
+            }
         }
 
         // {@link LatinIME#getSuggestedWords(int)} method calls with same session id have to
diff --git a/tests/src/com/android/inputmethod/latin/StringUtilsTests.java b/tests/src/com/android/inputmethod/latin/StringUtilsTests.java
index 5810abb..b6a05e9 100644
--- a/tests/src/com/android/inputmethod/latin/StringUtilsTests.java
+++ b/tests/src/com/android/inputmethod/latin/StringUtilsTests.java
@@ -101,7 +101,7 @@
                 StringUtils.capitalizeFirstCodePoint("aßa", Locale.GERMAN));
         assertEquals("Iab",
                 StringUtils.capitalizeFirstCodePoint("iab", Locale.ENGLISH));
-        assertEquals("cAmElCaSe",
+        assertEquals("CAmElCaSe",
                 StringUtils.capitalizeFirstCodePoint("cAmElCaSe", Locale.ENGLISH));
         assertEquals("İab",
                 StringUtils.capitalizeFirstCodePoint("iab", new Locale("tr")));