CSSStyleSheetResource should cache decoded text instead of raw bytes
Before this CL, CSSStyleSheetResource kept undecoded text alive, and
decoded text whenever it was requested.
After this CL, the decoded text is kept alive as cache.
It discards undecoded text when the whole sheet text is loaded to avoid
unnecessary memory usage.
As a side-effect, CSSStyleSheetResource::sheetText is no longer const,
as it may cache m_decodedSheetText.
BUG=642722, 653502
Review-Url: https://codereview.chromium.org/2290983003
Cr-Commit-Position: refs/heads/master@{#424941}
9 files changed
