Add possibility to ignore unregistered crash keys. Use this from WebView

android_webview/common/crash_reporter/crash_keys.cc

Index: android_webview/common/crash_reporter/crash_keys.cc
diff --git a/android_webview/common/crash_reporter/crash_keys.cc b/android_webview/common/crash_reporter/crash_keys.cc
index cd82afc34bb68a402c48d870c89d9344f8e29f08..c1a46ec32e6170a0c067d182a9e101c38e74e183 100644
--- a/android_webview/common/crash_reporter/crash_keys.cc
+++ b/android_webview/common/crash_reporter/crash_keys.cc
@@ -37,7 +37,8 @@ size_t RegisterWebViewCrashKeys() {
   std::vector<base::debug::CrashKey> keys(fixed_keys,
                                           fixed_keys + arraysize(fixed_keys));
 
-  return base::debug::InitCrashKeys(&keys.at(0), keys.size(), kChunkMaxLength);
+  return base::debug::InitCrashKeys(&keys.at(0), keys.size(), kChunkMaxLength,
+                                    true /* ignore_unregistered_keys */);
 }
 }