Update from chromium https://crrev.com/301315

base/BUILD.gn

Index: base/BUILD.gn
diff --git a/base/BUILD.gn b/base/BUILD.gn
index 556a09a21f73b68e9eafde14548e7db3bf8d962b..d94b4400107fd1bba26ec8313ea1a83343cfa974 100644
--- a/base/BUILD.gn
+++ b/base/BUILD.gn
@@ -329,7 +329,13 @@ component("base") {
     "memory/discardable_memory_mac.cc",
     "memory/discardable_memory_manager.cc",
     "memory/discardable_memory_manager.h",
+    "memory/discardable_memory_shmem.cc",
+    "memory/discardable_memory_shmem.h",
+    "memory/discardable_memory_shmem_allocator.cc",
+    "memory/discardable_memory_shmem_allocator.h",
     "memory/discardable_memory_win.cc",
+    "memory/discardable_shared_memory.cc",
+    "memory/discardable_shared_memory.h",
     "memory/linked_ptr.h",
     "memory/manual_constructor.h",
     "memory/memory_pressure_listener.cc",
@@ -1185,6 +1191,7 @@ test("base_unittests") {
     "memory/aligned_memory_unittest.cc",
     "memory/discardable_memory_manager_unittest.cc",
     "memory/discardable_memory_unittest.cc",
+    "memory/discardable_shared_memory_unittest.cc",
     "memory/linked_ptr_unittest.cc",
     "memory/ref_counted_memory_unittest.cc",
     "memory/ref_counted_unittest.cc",