[Contextual Search] Fix NPE when no Search Term.

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

 // Copyright 2015 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.app.Activity;
 import android.content.Context;
+import android.text.TextUtils;
 import android.view.View;
 import android.view.ViewGroup;
 import android.view.ViewTreeObserver;
 import android.view.ViewTreeObserver.OnGlobalFocusChangeListener;
 
 import org.chromium.base.ActivityState;
 import org.chromium.base.ApplicationStatus;
 import org.chromium.base.ApplicationStatus.ActivityStateListener;
 import org.chromium.base.SysUtils;
 import org.chromium.base.VisibleForTesting;
@@ skipping 705 matching lines @@
         }
         mSearchPanel.onSearchTermResolutionResponse(message);
 
         // If there was an error, fall back onto a literal search for the selection.
         // Since we're showing the panel, there must be a selection.
         if (doLiteralSearch) {
             searchTerm = mSelectionController.getSelectedText();
             alternateTerm = null;
             doPreventPreload = true;
         }
-        if (!searchTerm.isEmpty()) {
+        if (!TextUtils.isEmpty(searchTerm)) {
             // TODO(donnd): Instead of preloading, we should prefetch (ie the URL should not
             // appear in the user's history until the user views it).  See crbug.com/406446.
             boolean shouldPreload = !doPreventPreload && mPolicy.shouldPrefetchSearchResult(true);
             mSearchRequest = new ContextualSearchRequest(searchTerm, alternateTerm, shouldPreload);
             // Trigger translation, if enabled.
             if (!contextLanguage.isEmpty()) {
                 if (mPolicy.needsTranslation(contextLanguage, getReadableLanguages())) {
                     boolean doForceTranslate = !mPolicy.disableForceTranslationOnebox();
                     if (doForceTranslate) {
                         mSearchRequest.forceTranslation(contextLanguage,
@@ skipping 547 matching lines @@
     private native void nativeDestroy(long nativeContextualSearchManager);
     private native void nativeStartSearchTermResolutionRequest(long nativeContextualSearchManager,
             String selection, boolean useResolvedSearchTerm, ContentViewCore baseContentViewCore,
             boolean maySendBasePageUrl);
     private native void nativeGatherSurroundingText(long nativeContextualSearchManager,
             String selection, boolean useResolvedSearchTerm, ContentViewCore baseContentViewCore,
             boolean maySendBasePageUrl);
     private native String nativeGetTargetLanguage(long nativeContextualSearchManager);
     private native String nativeGetAcceptLanguages(long nativeContextualSearchManager);
 }