commit c56c2429b0f6970c05d630f05acf44b6ada2f346
author Hector Dearman <hjd@google.com> Tue Jul 03 09:50:03 2018 +0100
committer Hector Dearman <hjd@google.com> Tue Jul 03 09:50:03 2018 +0100
tree d65a635b815d7edec8093a280cc560697ced1647
parent ea4bcdc1e7f40770e068833fceda0ac3d4a97aa9

perfetto-ui: Plumb trace_processor to javascript

src/trace_processor/wasm_bridge.cc is our entry point to the
WASM code it exports an Initialize function and also one function for
each rpc in each proto service implemented by the trace_processor
(a subset of protos/perfetto/trace_processor/*).

The Initialize method takes two functions which are implemented on the
javascript side:
- reply
  This is how the trace_processor replies to rpc requests.
- read
  This is the interface the trace_processor uses to read parts of the
  trace file.

ui/src/engine/wasm_bridge.ts is the typescript counterpart to
wasm_bridge.cc. It lives in a dedicated worker thread.

Initialization flow is:
1) The worker thread (wasm.ts) starts up creating WasmBridge
2) this starts up the WASM
3) the worker calls WasmBridge#initialize
4) WasmBridge#initialize (asynchronously) waits for the WASM module
   to start up to complete (including WASM compilation)
5) WasmBridge#initialize (asynchronously) waits the file to arrive
6) WasmBridge#initialize calls the C++ initialize, the C++ begins
   reading the trace via the provided read method.
7) The C++ initialization is complete we call the reply method
8) The ts WasmBridge issues any calls to the WASM which had been
   queued while the C++ was setting up.

Change-Id: Iec86ea06124b0405d7cf16c509c37a5570406930