Add a linter that checks for copyright headers.

Makefile

 # Makefile debugging hack: uncomment the two lines below and make will tell you
 # more about what is happening.  The output generated is of the form
 # "FILE:LINE [TARGET (DEPENDENCIES) (NEWER)]" where DEPENDENCIES are all the
 # things TARGET depends on and NEWER are all the files that are newer than
 # TARGET.  DEPENDENCIES will be colored green and NEWER will be blue.
 #
 #OLD_SHELL := $(SHELL)
 #SHELL = $(warning [$@ ($^) ($?) ])$(OLD_SHELL)
 
 # Build a target for JavaScript files.  The find command excludes directories
@@ skipping 254 matching lines @@
 yuidoc-lint: $(JSFILES)
         bin/lint-yuidoc
 
 recess: node_modules/recess
         @# We need to grep for "Perfect" because recess does not set a
         @# non-zero exit code if it rejects a file.  If this fails, run the
         @# recess command below without the grep to get recess' report.
         node_modules/recess/bin/recess lib/views/stylesheet.less \
             --config recess.json | grep -q Perfect
 
-lint: test-prep jshint gjslint recess yuidoc-lint test-filtering
+lint: test-prep jshint gjslint recess lint-license-headers test-filtering \
+                yuidoc-lint
+
+lint-license-headers:
+        @# Take the list of JS files in one long line and break them into
+        @# multiple lines (this assumes there are no spaces in the paths).
+        @# Remove non-JS files, remove third-party files, and remove files in
+        @# the root of the project.  Finally, search for copyright notices in
+        @# the files and report files that do not have one.
+        echo $(JSFILES) | sed 's/ /\n/g' \
+        | grep '\.js$$' | grep -v /assets/ | grep / \
+        | xargs -I {} sh -c "grep -L '^Copyright (C) 2[^ ]* Canonical Ltd.' {}" \
+        || (echo "The above files are missing copyright headers."; false)
 
 virtualenv/bin/python:
         virtualenv virtualenv
 
 virtualenv/bin/gjslint virtualenv/bin/fixjsstyle: virtualenv/bin/python
         virtualenv/bin/easy_install archives/closure_linter-latest.tar.gz
 
 beautify: virtualenv/bin/fixjsstyle
         virtualenv/bin/fixjsstyle --strict --nojsdoc --jslint_error=all $(JSFILES)
 
@@ skipping 299 matching lines @@
 endif
 
 # targets are alphabetically sorted, they like it that way :-)
 .PHONY: beautify build build-files build-devel clean clean-all clean-deps \
         clean-docs code-doc debug devel docs dist gjslint help \
         install-npm-packages jshint lint main-doc npm-cache npm-cache-file \
         prep prod recess server spritegen test test-debug test-misc test-prep \
         test-prod undocumented view-code-doc view-docs view-main-doc yuidoc-lint
 
 .DEFAULT_GOAL := all