refactor find state and scrolling

Explicitly call webkit to note when find dialog is visible,
to dismiss the find dialog and clear to matches.

Companion fix in frameworks/base and external/webkit

http://b/2370069
diff --git a/src/com/android/browser/BrowserActivity.java b/src/com/android/browser/BrowserActivity.java
index 0bf370c..df80e99 100644
--- a/src/com/android/browser/BrowserActivity.java
+++ b/src/com/android/browser/BrowserActivity.java
@@ -1543,6 +1543,7 @@
                 }
                 mFindDialog.setWebView(getTopWindow());
                 mFindDialog.show();
+                getTopWindow().setFindIsUp(true);
                 mMenuState = EMPTY_MENU;
                 break;