devtools/madb: prefix console messages with device ids

This CL implements prefixer, an io.Writer wrapper that internally
buffers the output and adds the given prefix to each line of the
output.

madb exec command now uses this prefixer to distinguish console
messages coming from different devices.

Change-Id: I2ac3302bdadd9a781b80a94ebf3fa20a5e2cac62
3 files changed
tree: c0e0993578b8e228ec369d9fa0c98f3fb5de61ee
  1. doc.go
  2. exec.go
  3. madb.go
  4. madb_test.go
  5. prefixer.go
  6. prefixer_test.go