[SysApps] Reflect recent changes on Chromium upstream (8d368d625b)

Make the root_namespace argument to json_schema_compiler.gypi a string
pattern rather than a prefix.
[Runtime] StringToLowerASCII now it on the base:: namespace
[Runtime] content::ContentBrowserClient API changes

The Crosswalk Android fix needs to be verified. I assumed that
bridge->ShowNotification() call is synchronous.
[DevTools] Reflect the changes on content::DevToolsAgentHost API
Merge pull request #2340 from tmpsantos/next

M38 fixes