[ios] Automatically fail any WebTest whose render process crashes.

ios/web/public/test/web_test.mm

Index: ios/web/public/test/web_test.mm
diff --git a/ios/web/public/test/web_test.mm b/ios/web/public/test/web_test.mm
index 773261d23a72cf2920de78274dcfe66c2521e112..e3525b9d81908ea5385c981e0665a06e9a29d1c3 100644
--- a/ios/web/public/test/web_test.mm
+++ b/ios/web/public/test/web_test.mm
@@ -6,11 +6,24 @@
 
 #include "base/memory/ptr_util.h"
 #include "ios/web/public/active_state_manager.h"
+#include "ios/web/public/web_state/global_web_state_observer.h"
 #import "ios/web/public/test/fakes/test_web_client.h"
 
 namespace web {
 
-WebTest::WebTest() : web_client_(base::WrapUnique(new TestWebClient)) {}
+class WebTestRenderProcessCrashObserver : public GlobalWebStateObserver {
+ public:
+  WebTestRenderProcessCrashObserver() = default;
+  ~WebTestRenderProcessCrashObserver() override = default;
+
+  void RenderProcessGone(WebState* web_state) override {
+    FAIL() << "Renderer process died unexpectedly during the test";
+  }
+};
+
+WebTest::WebTest()
+    : web_client_(base::WrapUnique(new TestWebClient)),
+      crash_observer_(base::MakeUnique<WebTestRenderProcessCrashObserver>()) {}
 
 WebTest::~WebTest() {}
 
@@ -32,4 +45,12 @@ BrowserState* WebTest::GetBrowserState() {
   return &browser_state_;
 }
 
+void WebTest::SetIgnoreRenderProcessCrashesDuringTesting(bool allow) {
+  if (allow) {
+    crash_observer_ = nullptr;
+  } else {
+    crash_observer_ = base::MakeUnique<WebTestRenderProcessCrashObserver>();
+  }
+}
+
 }  // namespace web