Fix counting number of functions in Wasm Modules

This CL moves the recording of the number of functions in a Wasm
module to the size read in the "functions" section of the module. The
advantage is that all modules read this section once, making it a good
target for collecting the data.

The previous code was also broken because in one code path, it did not
distinguish between asm.js and Wasm modules.

Bug: v8:6361
Change-Id: I6c49e91975c1730608e791036d15622d538bce77
Reviewed-on: https://chromium-review.googlesource.com/600837Reviewed-by: Bill Budge <bbudge@chromium.org>
Commit-Queue: Karl Schimpf <kschimpf@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47168}

src/wasm/module-compiler.cc

@@ -576,10 +576,6 @@ MaybeHandle<WasmModuleObject> ModuleCompiler::CompileToModuleObjectInternal(
     temp_instance->function_code[i] = init_builtin;
   }
 
-  (module_->is_wasm() ? counters()->wasm_functions_per_wasm_module()
-                      : counters()->wasm_functions_per_asm_module())
-      ->AddSample(static_cast<int>(module_->functions.size()));
-
   if (!lazy_compile) {
     size_t funcs_to_compile =
         module_->functions.size() - module_->num_imported_functions;
@@ -2082,9 +2078,6 @@ class AsyncCompileJob::PrepareAndStartCompile : public CompileStep {
       job_->temp_instance_->function_code[i] = illegal_builtin;
     }
 
-    job_->counters()->wasm_functions_per_wasm_module()->AddSample(
-        static_cast<int>(module_->functions.size()));
-
     // Transfer ownership of the {WasmModule} to the {ModuleCompiler}, but
     // keep a pointer.
     WasmModule* module = module_.get();

src/wasm/module-decoder.cc

@@ -503,6 +503,9 @@ class ModuleDecoder : public Decoder {
   void DecodeFunctionSection() {
     uint32_t functions_count =
         consume_count("functions count", kV8MaxWasmFunctions);
+    (IsWasm() ? GetCounters()->wasm_functions_per_wasm_module()
+              : GetCounters()->wasm_functions_per_asm_module())
+        ->AddSample(static_cast<int>(functions_count));
     module_->functions.reserve(functions_count);
     module_->num_declared_functions = functions_count;
     for (uint32_t i = 0; ok() && i < functions_count; ++i) {