egl: add EGL_KHR_mutable_render_buffer

- Allow drivers to support it and applications to query for it.
- Add it to the platform header.

Bug 27129258

Change-Id: I7ce762f03889027d67803ba2da85a43584f3cf79
diff --git a/opengl/libs/EGL/eglApi.cpp b/opengl/libs/EGL/eglApi.cpp
index e7703d8..52f6859 100644
--- a/opengl/libs/EGL/eglApi.cpp
+++ b/opengl/libs/EGL/eglApi.cpp
@@ -115,6 +115,7 @@
         "EGL_KHR_partial_update "               // strongly recommended
         "EGL_EXT_buffer_age "                   // strongly recommended with partial_update
         "EGL_KHR_create_context_no_error "
+        "EGL_KHR_mutable_render_buffer "
         ;
 
 // extensions not exposed to applications but used by the ANDROID system