Save and restore state in the webview shell.

This exercises webview state save/restore, and also makes using the
shell as a testing/demonstration tool easier, because the current URL
is retained and reloaded when you switch webview providers.

BUG=
NOPRESUBMIT=true

Review-Url: https://codereview.chromium.org/2330013002
Cr-Commit-Position: refs/heads/master@{#418825}

android_webview/tools/system_webview_shell/apk/src/org/chromium/webview_shell/WebViewBrowserActivity.java

@@ -184,6 +184,23 @@ public class WebViewBrowserActivity extends Activity implements PopupMenu.OnMenu
 
         String url = getUrlFromIntent(getIntent());
         if (url == null) {
+            mWebView.restoreState(savedInstanceState);
+            url = mWebView.getUrl();
+            if (url != null) {
+                // If we have restored state, and that state includes
+                // a loaded URL, we reload. This allows us to keep the
+                // scroll offset, and also doesn't add an additional
+                // navigation history entry.
+                setUrlBarText(url);
+                // The immediately previous loadUrlFromurlbar must
+                // have got as far as calling loadUrl, so there is no
+                // URI parsing error at this point.
+                setUrlFail(false);
+                hideKeyboard(mUrlBar);
+                mWebView.reload();
+                mWebView.requestFocus();
+                return;
+            }
             // Make sure to load a blank page to make it immediately inspectable with
             // chrome://inspect.
             url = "about:blank";
@@ -193,6 +210,12 @@ public class WebViewBrowserActivity extends Activity implements PopupMenu.OnMenu
         loadUrlFromUrlBar(mUrlBar);
     }
 
+    @Override
+    public void onSaveInstanceState(Bundle savedInstanceState) {
+        // Deliberately don't catch TransactionTooLargeException here.
+        mWebView.saveState(savedInstanceState);
+    }
+
     @Override
     public void onBackPressed() {
         if (mWebView.canGoBack()) {