[Mac] Redo NSException handling, and generate better stacks for C++ exceptions.

base/mac/call_with_eh_frame_unittest.mm

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/mac/call_with_eh_frame.h"
+
+#import <Foundation/Foundation.h>
+
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace base {
+namespace mac {
+namespace {
+
+class CallWithEHFrameTest : public testing::Test {
+ protected:
+  void ThrowException() {
+    [NSArray arrayWithObject:nil];
+  }
+};
+
+// Catching from within the EHFrame is allowed.
+TEST_F(CallWithEHFrameTest, CatchExceptionHigher) {
+  bool __block saw_exception = false;
+  base::mac::CallWithEHFrame(^{
+    @try {
+      ThrowException();
+    } @catch (NSException* exception) {
+      saw_exception = true;
+    }
+  });
+  EXPECT_TRUE(saw_exception);
+}
+
+// Trying to catch an exception outside the EHFrame is blocked.
+TEST_F(CallWithEHFrameTest, CatchExceptionLower) {
+  auto catch_exception_lower = ^{
+    bool saw_exception = false;
+    @try {
+      base::mac::CallWithEHFrame(^{
+        ThrowException();
+      });
+    } @catch (NSException* exception) {
+      saw_exception = true;
+    }
+    ASSERT_FALSE(saw_exception);
+  };
+  EXPECT_DEATH(catch_exception_lower(), "");
+}
+
+}  // namespace
+}  // namespace mac
+}  // namespace base