Disable sandbox in content_browsertests

Adds the --no-sandbox flag to content_browsertests on
"Win10 Tets x64 (dbg)" in order to get information on the renderer
process crashes that are occurring on that configuration.

TBR=kbr@chromium.org

Bug: 1007013
Change-Id: I16174081881712e55af248b6dbc33a62c53e2605
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1952097Reviewed-by: Brian Sheedy <bsheedy@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Brian Sheedy <bsheedy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#721826}

testing/buildbot/chromium.win.json

@@ -3480,7 +3480,8 @@
       },
       {
         "args": [
-          "--disable-features=WebRTC-H264WithOpenH264FFmpeg"
+          "--disable-features=WebRTC-H264WithOpenH264FFmpeg",
+          "--no-sandbox"
         ],
         "experiment_percentage": 100,
         "merge": {

testing/buildbot/test_suite_exceptions.pyl

@@ -495,6 +495,9 @@
         # crbug.com/868082
         'args': [
           '--disable-features=WebRTC-H264WithOpenH264FFmpeg',
+          # TODO(https://crbug.com/1007013): Remove this flag when it's no
+          # longer necessary to figure out why the renderer process is crashing.
+          '--no-sandbox',
         ],
       },
       'Win10 Tests x64': {