diff --git a/deps/v8/include/v8-version.h b/deps/v8/include/v8-version.h
index 213d8805b86087..30a4182357505d 100644
--- a/deps/v8/include/v8-version.h
+++ b/deps/v8/include/v8-version.h
@@ -11,7 +11,7 @@
 #define V8_MAJOR_VERSION 9
 #define V8_MINOR_VERSION 3
 #define V8_BUILD_NUMBER 345
-#define V8_PATCH_LEVEL 16
+#define V8_PATCH_LEVEL 19
 
 // Use 1 for candidates and 0 otherwise.
 // (Boolean macro values are not supported by all preprocessors.)
diff --git a/deps/v8/src/compiler/js-native-context-specialization.cc b/deps/v8/src/compiler/js-native-context-specialization.cc
index 61fa46e94dfd41..30cab3ae26ac38 100644
--- a/deps/v8/src/compiler/js-native-context-specialization.cc
+++ b/deps/v8/src/compiler/js-native-context-specialization.cc
@@ -825,6 +825,12 @@ Reduction JSNativeContextSpecialization::ReduceGlobalAccess(
       return NoChange();
     } else if (property_cell_type == PropertyCellType::kUndefined) {
       return NoChange();
+    } else if (property_cell_type == PropertyCellType::kConstantType) {
+      // We rely on stability further below.
+      if (property_cell_value.IsHeapObject() &&
+          !property_cell_value.AsHeapObject().map().is_stable()) {
+        return NoChange();
+      }
     }
   } else if (access_mode == AccessMode::kHas) {
     DCHECK_EQ(receiver, lookup_start_object);
@@ -943,17 +949,7 @@ Reduction JSNativeContextSpecialization::ReduceGlobalAccess(
         if (property_cell_value.IsHeapObject()) {
           MapRef property_cell_value_map =
               property_cell_value.AsHeapObject().map();
-          if (property_cell_value_map.is_stable()) {
-            dependencies()->DependOnStableMap(property_cell_value_map);
-          } else {
-            // The value's map is already unstable. If this store were to go
-            // through the C++ runtime, it would transition the PropertyCell to
-            // kMutable. We don't want to change the cell type from generated
-            // code (to simplify concurrent heap access), however, so we keep
-            // it as kConstantType and do the store anyways (if the new value's
-            // map matches). This is safe because it merely prolongs the limbo
-            // state that we are in already.
-          }
+          dependencies()->DependOnStableMap(property_cell_value_map);
 
           // Check that the {value} is a HeapObject.
           value = effect = graph()->NewNode(simplified()->CheckHeapObject(),
diff --git a/deps/v8/testing/gmock/BUILD.gn b/deps/v8/testing/gmock/BUILD.gn
index de5ae539093257..c20d33511a1c1f 100644
--- a/deps/v8/testing/gmock/BUILD.gn
+++ b/deps/v8/testing/gmock/BUILD.gn
@@ -15,12 +15,7 @@ source_set("gmock") {
     "include/gmock/gmock-matchers.h",
     "include/gmock/gmock.h",
   ]
-  deps = [ "//third_party/googletest:gmock" ]
-
-  public_configs = [
-    "//third_party/googletest:gmock_config",
-    "//third_party/googletest:gtest_config",
-  ]
+  public_deps = [ "//third_party/googletest:gmock" ]
 }
 
 # The file/directory layout of Google Test is not yet considered stable. Until
diff --git a/deps/v8/tools/mb/mb.py b/deps/v8/tools/mb/mb.py
index 7031ba50dbdb4c..42ed60c7ef644b 100755
--- a/deps/v8/tools/mb/mb.py
+++ b/deps/v8/tools/mb/mb.py
@@ -53,6 +53,25 @@ def cmp(x, y):   # pylint: disable=redefined-builtin
     return (x > y) - (x < y)
 
 
+def _v8_builder_fallback(builder, builder_group):
+  """Fallback to V8 builder names before splitting builder/tester.
+
+  This eases splitting builders and testers on release branches and
+  can be removed as soon as all builder have been split and all MB configs
+  exist on all branches.
+  """
+  builders = [builder]
+  if builder.endswith(' - builder'):
+    builders.append(builder[:-len(' - builder')])
+  elif builder.endswith(' builder'):
+    builders.append(builder[:-len(' builder')])
+
+  for builder in builders:
+    if builder in builder_group:
+      return builder_group[builder]
+  return None
+
+
 def main(args):
   mbw = MetaBuildWrapper()
   return mbw.Main(args)
@@ -651,12 +670,14 @@ def ConfigFromArgs(self):
       raise MBErr('Builder groups name "%s" not found in "%s"' %
                   (self.args.builder_group, self.args.config_file))
 
-    if not self.args.builder in self.builder_groups[self.args.builder_group]:
+    config = _v8_builder_fallback(
+        self.args.builder, self.builder_groups[self.args.builder_group])
+
+    if not config:
       raise MBErr(
         'Builder name "%s"  not found under builder_groups[%s] in "%s"' %
         (self.args.builder, self.args.builder_group, self.args.config_file))
 
-    config = self.builder_groups[self.args.builder_group][self.args.builder]
     if isinstance(config, dict):
       if self.args.phase is None:
         raise MBErr('Must specify a build --phase for %s on %s' %