Expand CRX verifier to verify CRX₃ files.

components/crx_file/BUILD.gn

Index: components/crx_file/BUILD.gn
diff --git a/components/crx_file/BUILD.gn b/components/crx_file/BUILD.gn
index 65f108fd5542f615f2135fdce91293f6a9075d61..eff371f536a9c71ffc2bfd050f5950ebec40f3a5 100644
--- a/components/crx_file/BUILD.gn
+++ b/components/crx_file/BUILD.gn
@@ -2,6 +2,8 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//third_party/protobuf/proto_library.gni")
+
 static_library("crx_file") {
   sources = [
     "crx2_file.cc",
@@ -16,6 +18,10 @@ static_library("crx_file") {
     "//base",
     "//crypto",
   ]
+
+  public_deps = [
+    ":crx3_proto",
+  ]
 }
 
 source_set("unit_tests") {
@@ -30,3 +36,9 @@ source_set("unit_tests") {
     "//testing/gtest",
   ]
 }
+
+proto_library("crx3_proto") {
+  sources = [
+    "crx3.proto",
+  ]
+}