Accept b/ for bug IDs in ANGLE CLs.

Bug: b/151095080
Change-Id: Ic9da14a1476958eb00d4499dacdaa9c529b0626c
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2152849
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Geoff Lang <geofflang@chromium.org>

PRESUBMIT.py

@@ -43,8 +43,8 @@ def _CheckChangeHasBugField(input_api, output_api):
     if len(bugs) == 1 and bugs[0] == 'None':
         return []
 
-    projects = ['angleproject', 'chromium', 'dawn', 'fuchsia', 'skia', 'swiftshader', 'b']
-    bug_regex = re.compile(r"([a-z]+):(\d+)")
+    projects = ['angleproject:', 'chromium:', 'dawn:', 'fuchsia:', 'skia:', 'swiftshader:', 'b/']
+    bug_regex = re.compile(r"([a-z]+[:/])(\d+)")
     errors = []
     extra_help = None