When BackForwardCache is enabled the old RFH tree may be cached instead of being
immediately deleted as a result of main frame navigation. If a RFH is cached
then delivery of the CefFrameHandler::OnFrameDetached callback will be delayed
until the the RFH is ejected from the cache (possibly not occurring until the
browser is destroyed). This change in OnFrameDetached timing was causing
FrameHandlerTest.OrderSubCrossOrigin* to fail, and the inclusion of cached
frames in CefBrowserInfo::GetAllFrames was causing
FrameTest.NestedIframesDiffOrigin to fail.
BackForwardCache is currently being tested via field trials (see
https://crbug.com/1171298) and can be explicitly disabled using the
`--disable-back-forward-cache` or `--disable-features=BackForwardCache`
command-line flags.
See the new cef_frame_handler.h for complete usage documentation.
This change includes the following related enhancements:
- The newly added CefBrowser::IsValid method will return false (in the browser
process) after CefLifeSpanHandler::OnBeforeClose is called.
- CefBrowser::GetMainFrame will return a valid object (in the browser process)
until after CefLifeSpanHandler::OnBeforeClose is called.
- The main frame object will change during cross-origin navigation or
re-navigation after renderer process termination. During that time,
GetMainFrame will return the new/pending frame (in the browser process) and
any messages that arrive for the new/pending frame will be correctly
attributed in OnProcessMessageReceived.
- Commands to be executed in the renderer process that may fail during early
frame initialization (ExecuteJavaScript, LoadRequest, etc.) will now be
queued until after the JavaScript context for the frame has been created.
- Logging has been added for any commands that are dropped because they arrived
after frame detachment.
