EventListener is an interface that is used to listen for thread events.
Thread holds the state for a single thread of execution.
Frame holds a number of variable scopes for one of a thread's stack frame.
Scope is a container for frame variables.

Bug: b/145351270
Change-Id: Ic61e17f32cfd6929dbd7b0fce1ffb716301fc73e
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/38897Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Ben Clayton <bclayton@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>