Revert 152406 - Introduce shared_memory_support media target for PPAPI.

Revert 152406 - Introduce shared_memory_support media target for PPAPI.

Allows PPAPI to directly utilize shared memory utility code instead
of duplicating it and CHECK'ing for equivalency.

Required to eventually convert PPAPI to using an AudioBus and floats
in PPB_Audio_Shared::Run().  http://crbug.com/114700

BUG=123203
TEST=unittests


Review URL: https://chromiumcodereview.appspot.com/10826296

TBR=dalecurtis@chromium.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=152431