[wasm] Scrub all mentions of --wasm-jit-to-native flag.

R=titzer@chromium.org
BUG=v8:7549

Change-Id: I2b95a4d204dff6038b5a012b9753242f3384b886
Reviewed-on: https://chromium-review.googlesource.com/979811Reviewed-by: Ben Titzer <titzer@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52215}

src/frames.cc

@@ -445,10 +445,8 @@ StackFrame::Type StackFrame::ComputeType(const StackFrameIteratorBase* iterator,
     }
   } else {
     Address pc = *(state->pc_address);
-    // If FLAG_wasm_jit_to_native is disabled, we still have an empty
-    // wasm_code_manager, and this test will be false. This is easier to read
-    // than checking the flag, then getting the code, and then, if both are true
-    // (non-null, respectivelly), going down the wasm_code path.
+    // If the {pc} does not point into WebAssembly code we can rely on the
+    // returned {wasm_code} to be null and fall back to {GetContainingCode}.
     wasm::WasmCode* wasm_code =
         iterator->isolate()->wasm_engine()->code_manager()->LookupCode(pc);
     if (wasm_code != nullptr) {