[TEMP][IVI] WebGL: Turn off MSAA.

MSAA is disabled for now and will be enabled once known issues are fixed for IVI.

BUG=https://crosswalk-project.org/jira/browse/XWALK-1113
Merge pull request #9 from ds-hwang/webgl_msaa

[TEMP][IVI] WebGL: Turn off MSAA.