De-classicify Browser

Removes the hard run-time dependency on WebViewClassic.
(Still needs visisbility of it to build though)
This is needed to enable chromium webview testing.

Change-Id: I290b6b23b2eac525537ebc3ef8007d681a67a169
diff --git a/src/com/android/browser/Tab.java b/src/com/android/browser/Tab.java
index b5000c2..e3a0333 100644
--- a/src/com/android/browser/Tab.java
+++ b/src/com/android/browser/Tab.java
@@ -1293,7 +1293,9 @@
             // does a redirect after a period of time. The user could have
             // switched to another tab while waiting for the download to start.
             mMainView.setDownloadListener(mDownloadListener);
-            getWebViewClassic().setWebBackForwardListClient(mWebBackForwardListClient);
+            if (BrowserWebView.isClassic()) {
+                getWebViewClassic().setWebBackForwardListClient(mWebBackForwardListClient);
+            }
             TabControl tc = mWebViewController.getTabControl();
             if (tc != null && tc.getOnThumbnailUpdatedListener() != null) {
                 mMainView.setPictureListener(this);
@@ -1535,6 +1537,9 @@
      * @return The main WebView of this tab.
      */
     WebViewClassic getWebViewClassic() {
+        if (!BrowserWebView.isClassic()) {
+            return null;
+        }
         return WebViewClassic.fromWebView(mMainView);
     }