added blackboxing doc and blackboxing assets
removed needless images. added note about filing a bug at bottom
Merge github.com:GoogleChrome/devtools-docs into blackboxing

* github.com:GoogleChrome/devtools-docs:
  Improve formatting of contributing.md
  Fix typo
  Update remote-debugging.html
combine call stack screens
combine context menu screens
Merge github.com:GoogleChrome/devtools-docs into blackboxing

* github.com:GoogleChrome/devtools-docs:
  Quick fix on image for homepage to bypass cache
WebView'ssize -> WebView's size
Merge pull request #170 from davidcalhoun/patch-1

Space typo: WebView'ssize -> WebView's size
Fix youtube link
Merge pull request #172 from harshadsabne/master

Fix youtube link
contributing guide. move depot tools stuff down. cleanup and user-profile-dir changeup.
Merge pull request #162 from jaredwilli/blackboxing

Added blackboxing doc and blackboxing assets
blackboxing: removing screenr for now

We'l want to add a more complete video however.
fix hhttps in link. ref #64
Fixed typo in readme

“Troubleshooting” was missing “e”.
Merge pull request #175 from PoziWorld/patch-1

Fixed typo in readme
`contributing.md`: Fix link
Losslessly minify all images
removing old device mode files
adding updated device mode files