[v8][wasm] Add a fuzzer for the async compilation pipeline.

Hi Max, to make up for the fuzzer I removed I add a new fuzzer now. The
new fuzzer tests the async compilation pipeline of WebAssembly.

In addition I cleaned up the dictionary used by the v8_wasm_fuzzer and
the new fuzzer. The content was quite out-dated.

R=mmoroz@chromium.org

Change-Id: Idd0e9a9649d666f4e15fbed821e48aa9143fbbaf
Reviewed-on: https://chromium-review.googlesource.com/541381Reviewed-by: Max Moroz <mmoroz@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#480832}

testing/libfuzzer/fuzzers/BUILD.gn

@@ -290,6 +290,16 @@ fuzzer_test("v8_wasm_fuzzer") {
   libfuzzer_options = [ "max_len=500" ]
 }
 
+fuzzer_test("v8_wasm_async_fuzzer") {
+  sources = []
+  deps = [
+    "//v8:wasm_async_fuzzer",
+  ]
+  dict = "dicts/v8_wasm.dict"
+  seed_corpus = "//v8/test/fuzzer/wasm_corpus/"
+  libfuzzer_options = [ "max_len=500" ]
+}
+
 fuzzer_test("v8_wasm_asmjs_fuzzer") {
   sources = []
   deps = [

testing/libfuzzer/fuzzers/dicts/v8_wasm.dict

-wasm_magic="\x6d\x73\x61\x00"
-"memory"
-"\x06memory"
-"signatures"
-"\x0asignatures"
-"functions"
-"\x09functions"
-"globals"
-"\x07globals"
-"data_segments"
-"\x0ddata_segments"
-"function_table"
-"\x0efunction_table"
-"end"
-"\x03end"
-"start_function"
-"\x0estart_function"
-"import_table"
-"\x0cimport_table"
-"export_table"
-"\x0cexport_table"
-"function_signatures"
-"\x13function_signatures"
-"function_bodies"
-"\x0ffunction_bodies"
-"names"
-"\x05names"
-"\x00\x00\x00\x00\x00\x00\x00\x00"
-"\x02\x00"
+"name"