[wasm] Split the wasm compilation into two phases for parallel compilation.

src/compiler/wasm-compiler.h

Index: src/compiler/wasm-compiler.h
diff --git a/src/compiler/wasm-compiler.h b/src/compiler/wasm-compiler.h
index 0a47f61745e0da4a14de728f8cb23af277ff6fd0..ee7f521c9fc23d42b79a4a4f359d1e6e44a147b6 100644
--- a/src/compiler/wasm-compiler.h
+++ b/src/compiler/wasm-compiler.h
@@ -55,14 +55,14 @@ Handle<JSFunction> CompileJSToWasmWrapper(
 
 WasmCompilationUnit* CreateWasmCompilationUnit(
     wasm::ErrorThrower* thrower, Isolate* isolate, wasm::ModuleEnv* module_env,
-    const wasm::WasmFunction* function);
+    const wasm::WasmFunction* function, uint32_t index);
 
 void ExecuteCompilation(WasmCompilationUnit* unit);
 
-int GetIndexOfWasmCompilationUnit(WasmCompilationUnit* unit);
-
 Handle<Code> FinishCompilation(WasmCompilationUnit* unit);
 
+uint32_t GetIndexOfWasmCompilationUnit(WasmCompilationUnit* unit);
+
 // Abstracts details of building TurboFan graph nodes for WASM to separate
 // the WASM decoder from the internal details of TurboFan.
 class WasmTrapHelper;