Add --browserhtml/-b command to ./mach run

This will run Servo with browser.html. We use the latest package in the
dependency tree if there are multiple copies, since there is no way for
Cargo to tell us which one is canonical.

python/servo/post_build_commands.py

@@ -9,6 +9,7 @@
 
 from __future__ import print_function, unicode_literals
 
+from glob import glob
 import os
 import os.path as path
 import subprocess
@@ -32,6 +33,18 @@ def read_file(filename, if_exists=False):
         return f.read()
 
 
+def find_dep_path_newest(package, bin_path):
+    deps_path = path.join(path.split(bin_path)[0], "build")
+    with cd(deps_path):
+        print(os.getcwd())
+        candidates = glob(package + '-*')
+    candidates = (path.join(deps_path, c) for c in candidates)
+    candidate_times = sorted(((path.getmtime(c), c) for c in candidates), reverse=True)
+    if len(candidate_times) > 0:
+        return candidate_times[0][1]
+    return None
+
+
 @CommandProvider
 class PostBuildCommands(CommandBase):
     @Command('run',
@@ -50,10 +63,12 @@ class PostBuildCommands(CommandBase):
                           'have no effect without this.')
     @CommandArgument('--debugger', default=None, type=str,
                      help='Name of debugger to use.')
+    @CommandArgument('--browserhtml', '-b', action='store_true',
+                     help='Launch with Browser.html')
     @CommandArgument(
         'params', nargs='...',
         help="Command-line arguments to be passed through to Servo")
-    def run(self, params, release=False, dev=False, android=None, debug=False, debugger=None):
+    def run(self, params, release=False, dev=False, android=None, debug=False, debugger=None, browserhtml=False):
         env = self.build_env()
         env["RUST_BACKTRACE"] = "1"
 
@@ -110,6 +125,13 @@ def run(self, params, release=False, dev=False, android=None, debug=False, debug
             # Prepend the debugger args.
             args = ([command] + self.debuggerInfo.args +
                     args + params)
+        elif browserhtml:
+            browserhtml_path = find_dep_path_newest('browserhtml', args[0])
+            if browserhtml_path is None:
+                print("Could not find browserhtml package; perhaps you haven't built Servo.")
+                return 1
+            args = args + ['-w', '-b', '--pref', 'dom.mozbrowser.enabled',
+                           path.join(browserhtml_path, 'out', 'index.html')]
         else:
             args = args + params