Add memory pressure dispatching callback to MemoryCoordinator

components/BUILD.gn

Index: components/BUILD.gn
diff --git a/components/BUILD.gn b/components/BUILD.gn
index 5e32036a4b90cd32b4d464ce90dda585f94810ed..d4924a472744ff9ff8db3f48bccfddd83bf38333 100644
--- a/components/BUILD.gn
+++ b/components/BUILD.gn
@@ -184,6 +184,7 @@ test("components_unittests") {
       "//components/invalidation/impl:unit_tests",
       "//components/keyed_service/content:unit_tests",
       "//components/link_header_util:unit_tests",
+      "//components/memory_coordinator/browser:unit_tests",
       "//components/memory_coordinator/child:unit_tests",
       "//components/navigation_interception:unit_tests",
       "//components/network_hints/renderer:unit_tests",
@@ -224,7 +225,7 @@ test("components_unittests") {
     deps += [ ":components_tests_pak_bundle_data" ]
   }
 
-  if (is_mac) {
+  if (is_mac || is_linux) {
     data_deps += [ "//content/shell:pak" ]
   }