Add hotkeys to Observatory debugger.
Add hotkeys to Observatory debugger.

Add 'cls' command to clear the console.

From 'help hotkeys':

List of hotkeys:

[TAB]        - complete a command
[Up Arrow]   - history previous
[Down Arrow] - history next

[Page Up]    - move up one frame
[Page Down]  - move down one frame

[F7]         - continue execution of the current isolate
[Ctrl ;]     - pause execution of the current isolate

[F8]         - toggle breakpoint at current location
[F9]         - next
[F10]        - step

BUG=24010
R=johnmccutchan@google.com

Review URL: https://codereview.chromium.org//1270283003 .

dartino/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk