* refactor: convert Menu and globalShortcut to gin
* refactor: convert api::Cookies to gin
* refactor: convert View and WebContentsView to gin
* refactor: convert WebContents related classes to gin
* refactor: convert powerMonitor to gin
* refactor: prepare for header change
* refactor: remove last uses of mate::EventEmitter
* refactor: remove mate::EventEmitter
* refactor: move trackable_object to gin_helper
* fix: custom converter should not use Handle
* fix: no more need to check if icon is empty
It was a bug that the Handle<NativeImage> can be non-empty when the
image file does not exist. The bug was caused by the converter code
writing out the image even when the convertion fails.
The bug was work-arounded by adding an additional check, but since the
original bug had been fixed, the additional check is no longer needed.
* fix: should always set frameId even when callback is null
* fix: do not mix gin/mate handles for NativeImage
* fix: fill uploadData property
* fix: requestHeaders in onBeforeSendHeaders
* fix: responseHeaders in onHeadersReceived
* fix: header keys should not be lowercased
* fix: gin::Dictionary::Get succeeds even though key does not exist...
* fix: throw for invalid filters
* test: re-enable api-web-request-spec
* chore: do not use deprecated base::Value API
