Updates to build tools in upstream CEF (sccache, --fast-update and others)

[cztomczak]

See if if we should implement any of the new flags to our build tools as well. See:

1. https://github.com/mozilla/sccache
2. https://bitbucket.org/chromiumembedded/cef/issues/2432/add-support-for-building-with-sccache
3. https://bitbucket.org/chromiumembedded/cef/issues/2435/support-more-frequent-chromium-master

The --fast-update option may not work correctly with cefpython's automate.py tool, since this tool creates cef/ and src/cef/ directories on its own (to be able to update CEF patches) and sets --no-cef-update flag. When analyzing automate-git.py and you find comparison cef_dir == cef_src_dir it is equivalent to if --fast-update.

New options in upstream automate-git.py tool:

+parser.add_option('--fast-update',
+                  action='store_true', dest='fastupdate', default=False,
+                  help='Update existing Chromium/CEF checkouts for fast incremental '+\
+                       'builds by attempting to minimize the number of modified files. '+\
+                       'The update will fail if there are unstaged CEF changes or if '+\
+                       'Chromium changes are not included in a patch file.')

+parser.add_option(
+    '--force-patch-update',
+    action='store_true',
+    dest='forcepatchupdate',
+    default=False,
+    help='Force update of patch files.')

+parser.add_option(
+    '--resave',
+    action='store_true',
+    dest='resave',
+    default=False,
+    help='Resave patch files.')

+parser.add_option(
+    '--build-failure-limit',
+    dest='buildfailurelimit',
+    default=1,
+    type="int",
+    help='Keep going until N jobs fail.')

# For building master branch

+parser.add_option('--chromium-channel', dest='chromiumchannel',
+                  help='Chromium channel to check out (canary, dev, beta or '+\
+                       'stable). This overrides the value specified by CEF '+\
+                       'in CHROMIUM_BUILD_COMPATIBILITY.txt.',
+                  default='')

+parser.add_option('--chromium-channel-distance', dest='chromiumchanneldistance',
+                  help='The target number of commits to step in the '+\
+                       'channel, or 0 to use the newest channel version. '+\
+                       'Used in combination with --chromium-channel.',
+                  default='')

# Other dev flags

+parser.add_option(
+    '--log-chromium-changes',
+    action='store_true',
+    dest='logchromiumchanges',
+    default=False,
+    help='Create a log of the Chromium changes.')