Android: Add comment to JavaExceptionReporter

Clarify the purpose of ensuring that the browser process crashes in java
rather than in native: for webview embedding apps.

Bug: None
Change-Id: I3cd847bc5a32e56ee429cd8d4ce41efa13d32209
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2064782
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Bo <boliu@chromium.org>
Auto-Submit: Peter Wen <wnwen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#742945}

base/android/java_exception_reporter.cc

@@ -32,6 +32,11 @@ LazyInstance<JavaExceptionFilter>::Leaky g_java_exception_filter;
 
 void InitJavaExceptionReporter() {
   JNIEnv* env = base::android::AttachCurrentThread();
+  // Since JavaExceptionReporter#installHandler will chain through to the
+  // default handler, the default handler should cause a crash as if it's a
+  // normal java exception. Prefer to crash the browser process in java rather
+  // than native since for webview, the embedding app may have installed its
+  // own JavaExceptionReporter handler and would expect it to be called.
   constexpr bool crash_after_report = false;
   SetJavaExceptionFilter(
       base::BindRepeating([](const JavaRef<jthrowable>&) { return true; }));