[omnibox] Limit search suggest parser fuzzer input size

There were some reported oom's, so curb size to something reasonable.
This CL only affects the fuzzer.

Bug: 1018506, 1018522
Change-Id: I051da49d510fb108dea95925104c839d11ef5aa2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1883871Reviewed-by: Tommy Li <tommycli@chromium.org>
Commit-Queue: Kevin Bailey <krb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#709902}

components/omnibox/browser/search_suggestion_parser_fuzzer.cc

@@ -23,6 +23,10 @@ struct IcuEnvironment {
 IcuEnvironment icu_env;
 
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
+  // This is an arbitrary size, and arguably even small for a JSON input,
+  // but we have to cut it off somewhere.
+  if (size > 4096)
+    return 0;
   std::unique_ptr<std::string> response_body =
       std::make_unique<std::string>(reinterpret_cast<const char*>(data), size);
   std::unique_ptr<base::Value> value(