Extract the shell runner into devtools.

README.md

Index: README.md
diff --git a/README.md b/README.md
index 64dbec844c5766586c8b188ad517f1d2bbb66664..d592c4da0246bd30b7f37b21808d9f70448e836d 100644
--- a/README.md
+++ b/README.md
@@ -212,20 +212,20 @@ $ mojo/tools/mojob.py dartcheck
 
 ## Run Mojo Shell
 
-`mojo_shell.py` is a universal shell runner abstracting away the differences
-between running on Linux and Android. Having built Mojo as described above, a
-demo app can be run as follows:
+Devtools script `mojo_shell` is a universal shell runner abstracting away the
+differences between running on Linux and Android. Having built Mojo as
+described above, a demo app can be run as follows:
 
 ```
-mojo/tools/mojo_shell.py mojo:spinning_cube  # Linux.
-mojo/tools/mojo_shell.py mojo:spinning_cube  --android # Android.
+mojo/devtools/common/mojo_shell mojo:spinning_cube  # Linux.
+mojo/devtools/common/mojo_shell mojo:spinning_cube  --android # Android.
 ```
 
 Pass `--sky path_to_sky_file` to run a
 [Sky](https://github.com/domokit/mojo/tree/master/sky) app on either platform:
 ```
-mojo/tools/mojo_shell.py --sky sky/examples/raw/hello_world.dart
-mojo/tools/mojo_shell.py --sky sky/examples/raw/hello_world.dart --android
+mojo/devtools/common/mojo_shell --sky sky/examples/raw/hello_world.dart
+mojo/devtools/common/mojo_shell --sky sky/examples/raw/hello_world.dart --android
 ```
 
 Passing the `-v` flag will increase the output verbosity. In particular, it will
@@ -249,8 +249,8 @@ start
 and retrieve the result:
 
 ```
-devtools/common/debugger tracing start
-devtools/common/debugger tracing stop [result.json]
+mojo/devtools/common/debugger tracing start
+mojo/devtools/common/debugger tracing stop [result.json]
 ```
 
 The trace file can be then loaded using the trace viewer in Chrome available at
@@ -299,14 +299,6 @@ running shell on the device) will not work unless the device is rooted and
 running a userdebug build. For Googlers, [follow the instructions at this
 link](http://go/mojo-internal-build-instructions).
 
-#### Aw, snap!
-
-If the shell crashes on the device, you won't see symbols. Use
-`tools/android_stack_parser/stack` to map back to symbols, e.g.:
-```
-adb logcat | ./tools/android_stack_parser/stack
-```
-
 ### Running manually on Linux
 
 If you wish to, you can also run the Linux Mojo shell directly with no wrappers: