Default to 1 when --force-device-scale-factor has an invalid value.

Currently, the scaling factor may end up as 0, causing a divide by 0.
Also add warnings to base::StringToFoo().

BUG=517944

Review URL: https://codereview.chromium.org/1278173006

Cr-Commit-Position: refs/heads/master@{#342505}


CrOS-Libchrome-Original-Commit: 62d4c69ec6bfaff365d9b240c1519802ddd245ab
1 file changed
tree: e27d35072e9282ed987bdd183999844f9f9254e7
  1. base/
  2. build/
  3. components/
  4. dbus/
  5. device/
  6. ipc/
  7. mojo/
  8. testing/
  9. third_party/
  10. ui/