[Chromecast] Disable ProxyScriptFetcherImplTest.HttpMimeType.
[Chromecast] Disable ProxyScriptFetcherImplTest.HttpMimeType.

ProxyScriptFetcherImplTest.HttpMimeType is flaky. Since proxy
script support isn't a huge priority, disable test for now.

BUG=internal b/19848784
R=gunsch@chromium.org

Review URL: https://codereview.chromium.org/1036683002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#322109}

chuan9/chromium-crosswalk,Fireblend/chromium-crosswalk,Pluto-tv/chromium-crosswalk,chuan9/chromium-crosswalk,Pluto-tv/chromium-crosswalk,hgl888/chromium-crosswalk,chuan9/chromium-crosswalk,ltilve/chromium,Fireblend/chromium-crosswalk,chuan9/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,Just-D/chromium-1,Pluto-tv/chromium-crosswalk,Chilledheart/chromium,TheTypoMaster/chromium-crosswalk,axinging/chromium-crosswalk,hgl888/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,Chilledheart/chromium,axinging/chromium-crosswalk,ltilve/chromium,hgl888/chromium-crosswalk,Pluto-tv/chromium-crosswalk,ltilve/chromium,axinging/chromium-crosswalk,ltilve/chromium,hgl888/chromium-crosswalk,Just-D/chromium-1,fujunwei/chromium-crosswalk,Just-D/chromium-1,Pluto-tv/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,ltilve/chromium,Fireblend/chromium-crosswalk,axinging/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,fujunwei/chromium-crosswalk,Chilledheart/chromium,chuan9/chromium-crosswalk,Fireblend/chromium-crosswalk,axinging/chromium-crosswalk,Pluto-tv/chromium-crosswalk,fujunwei/chromium-crosswalk,Chilledheart/chromium,PeterWangIntel/chromium-crosswalk,Just-D/chromium-1,hgl888/chromium-crosswalk,axinging/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,chuan9/chromium-crosswalk,Chilledheart/chromium,axinging/chromium-crosswalk,chuan9/chromium-crosswalk,Chilledheart/chromium,Fireblend/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,Just-D/chromium-1,Just-D/chromium-1,ltilve/chromium,TheTypoMaster/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,fujunwei/chromium-crosswalk,Fireblend/chromium-crosswalk,Chilledheart/chromium,fujunwei/chromium-crosswalk,Fireblend/chromium-crosswalk,Just-D/chromium-1,Just-D/chromium-1,hgl888/chromium-crosswalk,fujunwei/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,chuan9/chromium-crosswalk,ltilve/chromium,axinging/chromium-crosswalk,ltilve/chromium,fujunwei/chromium-crosswalk,hgl888/chromium-crosswalk,Pluto-tv/chromium-crosswalk,fujunwei/chromium-crosswalk,Fireblend/chromium-crosswalk,Fireblend/chromium-crosswalk,ltilve/chromium,TheTypoMaster/chromium-crosswalk,hgl888/chromium-crosswalk,hgl888/chromium-crosswalk,chuan9/chromium-crosswalk,Chilledheart/chromium,TheTypoMaster/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,axinging/chromium-crosswalk,Pluto-tv/chromium-crosswalk,axinging/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,fujunwei/chromium-crosswalk,Pluto-tv/chromium-crosswalk,axinging/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,Chilledheart/chromium,Just-D/chromium-1