PPAPI: Make GetProxiedInterface not re-enter the plugin
It's important that we never re-enter the plugin when it is blocked on
synchronous calls to the renderer (unless they are scripting messages, which
have to be re-entrant). This especially breaks assumptions in OpenGL usage.
This required making the plugin side of the PPB_VideoDecoder_Dev proxy check
for the interface prior to sending its synchronous Create message. I audited
all the other uses of GetProxiedInterface from the renderer, and none of the
others happen as a result of a sync plugin->renderer message.
I also renamed the existing "SupportsInterface" message to "IsInterfaceSupported" to make the intent more obvious, and because I liked the SupportsInterface name better for the new usage: Telling the renderer that an interface is supported.
BUG=418651
Review URL: https://codereview.chromium.org/
704913002
Cr-Commit-Position: refs/heads/master@{#303247}