GWP-ASan: Refactor multiprocess test wait

Use WaitForMultiprocessTestChildExit() instead of
base::Process::WaitForExitWithTimeout() to wait for multiprocess test
child processes to complete. It's identical to WaitForExitWithTimeout()
on macOS/Windows/Linux but also works on Android. (Android tests don't
fork so they use a special process monitoring mechanism.)

Bug: 973167
Change-Id: I3c3f10a155d4ea9058404ae7474cfacdcf2ed402
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1668335
Auto-Submit: Vlad Tsyrklevich <vtsyrklevich@chromium.org>
Commit-Queue: Vitaly Buka <vitalybuka@chromium.org>
Reviewed-by: Vitaly Buka <vitalybuka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#671908}

components/gwp_asan/client/sampling_malloc_shims_unittest.cc

@@ -76,8 +76,8 @@ class SamplingMallocShimsTest : public base::MultiProcessTest {
   void runTest(const char* name) {
     base::Process process = SpawnChild(name);
     int exit_code = -1;
-    ASSERT_TRUE(process.WaitForExitWithTimeout(
-        TestTimeouts::action_max_timeout(), &exit_code));
+    ASSERT_TRUE(WaitForMultiprocessTestChildExit(
+        process, TestTimeouts::action_max_timeout(), &exit_code));
     EXPECT_EQ(exit_code, kSuccess);
   }
 };

components/gwp_asan/client/sampling_partitionalloc_shims_unittest.cc

@@ -63,8 +63,8 @@ class SamplingPartitionAllocShimsTest : public base::MultiProcessTest {
   void runTest(const char* name) {
     base::Process process = SpawnChild(name);
     int exit_code = -1;
-    ASSERT_TRUE(process.WaitForExitWithTimeout(
-        TestTimeouts::action_max_timeout(), &exit_code));
+    ASSERT_TRUE(WaitForMultiprocessTestChildExit(
+        process, TestTimeouts::action_max_timeout(), &exit_code));
     EXPECT_EQ(exit_code, kSuccess);
   }
 };

components/gwp_asan/crash_handler/crash_handler_unittest.cc

@@ -224,8 +224,8 @@ class CrashHandlerTest : public base::MultiProcessTest,
         base::SpawnMultiProcessTestChild("CrashingProcess", cmd_line, options);
 
     int exit_code = -1;
-    EXPECT_TRUE(process.WaitForExitWithTimeout(
-        TestTimeouts::action_max_timeout(), &exit_code));
+    EXPECT_TRUE(WaitForMultiprocessTestChildExit(
+        process, TestTimeouts::action_max_timeout(), &exit_code));
     EXPECT_NE(exit_code, kSuccess);
 
     return (exit_code != kSuccess);