Web Automation: implicit navigations don't cause browsing context switch

Web Automation: implicit navigations don't cause browsing context switch
https://bugs.webkit.org/show_bug.cgi?id=174633
<rdar://problem/33387797>

Reviewed by Brian Burg.

When a new page load replaces the current frameset, for example when a link in the current browser context has a
_top target, there's no explicit context switch, so the web driver doesn't know that the current browsing
context is no longer valid. Following commands will still be using the previous frame as the current browsing
context, but they don't fail with no such frame because the frame is still alive in the page cache and
referenced in the internal maps used in both UI and web processes. This causes test
testShouldFocusOnTheReplacementWhenAFrameFollowsALinkToA_TopTargetedPage to fail, since it expects a no such
frame exception. When a new page navigation happens we can simply remove references to frames from
m_handleWebFrameMap in WebAutomationSession, because any existing frame reference in the map should be for a
previous page. With this, before the next command is executed, waitForNavigationToComplete will be called and it
will fail with no such frame, condition that is handled to switch to the top level browser context. The test
still fails, because the find element command is called with the top level browsing context, returning no such
element, instead of no such frame. This is consistent with Chrome.

* UIProcess/Automation/WebAutomationSession.cpp:
(WebKit::WebAutomationSession::navigationOccurredForFrame): Clear the m_handleWebFrameMap when a new page load
finished.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@219723 268f45cc-cd09-0410-ab3c-d52691b4dbfc