54640 Allow WIllPopCallback to return null or false to veto the pop. (cla: yes, f: material design, framework, waiting for tree to go green)

54670 Updated Nested SingleChildScrollView test for clarity (cla: yes, framework, waiting for tree to go green)

54674 Add searchFieldStyle (cla: yes, f: material design, framework, waiting for tree to go green)

54698 Allow headers to be passed to the WebSocket connection for VMServiceFlutterDriver (a: tests, cla: yes, framework, waiting for tree to go green)

54706 Wire in focusNode, focusColor, autofocus, and dropdownColor to DropdownButtonFormField (cla: yes, f: material design, framework, waiting for tree to go green)

54714 [Material] Added BottomNavigationBarTheme (cla: yes, f: material design, framework, waiting for tree to go green)