Navigation buttons should not enable if user can not navigate

content/shell/android/java/src/org/chromium/content_shell/Shell.java

 // Copyright 2012 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.content_shell;
 
 import android.content.Context;
 import android.graphics.drawable.ClipDrawable;
 import android.text.TextUtils;
 import android.util.AttributeSet;
@@ skipping 143 matching lines @@
             }
         });
         mUrlTextView.setOnFocusChangeListener(new OnFocusChangeListener() {
             @Override
             public void onFocusChange(View v, boolean hasFocus) {
                 setKeyboardVisibilityForUrl(hasFocus);
                 mNextButton.setVisibility(hasFocus ? GONE : VISIBLE);
                 mPrevButton.setVisibility(hasFocus ? GONE : VISIBLE);
                 if (!hasFocus) {
                     mUrlTextView.setText(mContentViewCore.getUrl());
+                    mPrevButton.setEnabled(mContentViewCore.canGoBack());
+                    mNextButton.setEnabled(mContentViewCore.canGoForward());
                 }
             }
         });
     }
 
     /**
      * Loads an URL.  This will perform minimal amounts of sanitizing of the URL to attempt to
      * make it valid.
      *
      * @param url The URL to be loaded by the shell.
@@ skipping 45 matching lines @@
     @CalledByNative
     private void onUpdateUrl(String url) {
         mUrlTextView.setText(url);
     }
 
     @SuppressWarnings("unused")
     @CalledByNative
     private void onLoadProgressChanged(double progress) {
         removeCallbacks(mClearProgressRunnable);
         mProgressDrawable.setLevel((int) (10000.0 * progress));
-        if (progress == 1.0) postDelayed(mClearProgressRunnable, COMPLETED_PROGRESS_TIMEOUT_MS);
+        if (progress == 1.0) {
+            postDelayed(mClearProgressRunnable, COMPLETED_PROGRESS_TIMEOUT_MS);
+            mPrevButton.setEnabled(mContentViewCore.canGoBack());

[Ted C, 2014/05/20 22:29:37]

In my previous comment, I meant that we should actually be hooking directly into
PlatformEnableUIControl in shell_android.cc.  Currently that method is empty,
but we should just add a new method in java:

@CalledByNative
private void enableUiControl(int controlId, boolean enabled) {
    if (controlId == 0) mPrevButton.setEnabled(enabled);
    else if (controlId == 1) mNextButton.setEnabled(enabled);
}

Then we just call that from shell_android and that keeps the android port closer
to the other platforms.

+            mNextButton.setEnabled(mContentViewCore.canGoForward());
+        }
     }
 
     @CalledByNative
     private void toggleFullscreenModeForTab(boolean enterFullscreen) {
     }
 
     @CalledByNative
     private boolean isFullscreenForTabOrPending() {
         return false;
     }
@@ skipping 46 matching lines @@
                 Context.INPUT_METHOD_SERVICE);
         if (visible) {
             imm.showSoftInput(mUrlTextView, InputMethodManager.SHOW_IMPLICIT);
         } else {
             imm.hideSoftInputFromWindow(mUrlTextView.getWindowToken(), 0);
         }
     }
 
     private static native void nativeCloseShell(long shellPtr);
 }