Do not obfuscate hamcrest classes

third_party/hamcrest/BUILD.gn

Index: third_party/hamcrest/BUILD.gn
diff --git a/third_party/hamcrest/BUILD.gn b/third_party/hamcrest/BUILD.gn
index 3680c1017250fdc531d6929a096893c44344f701..3c0c4d4ed3f6fd731df3418558c2479caf2db25c 100644
--- a/third_party/hamcrest/BUILD.gn
+++ b/third_party/hamcrest/BUILD.gn
@@ -17,16 +17,19 @@ java_prebuilt("hamcrest_core_java") {
   supports_android = true
   testonly = true
   jar_path = "lib/hamcrest-core-1.3.jar"
+  proguard_configs = [ "//third_party/hamcrest/proguard.flags" ]
 }
 
 java_prebuilt("hamcrest_integration_java") {
   supports_android = true
   testonly = true
   jar_path = "lib/hamcrest-integration-1.3.jar"
+  proguard_configs = [ "//third_party/hamcrest/proguard.flags" ]
 }
 
 java_prebuilt("hamcrest_library_java") {
   supports_android = true
   testonly = true
   jar_path = "lib/hamcrest-library-1.3.jar"
+  proguard_configs = [ "//third_party/hamcrest/proguard.flags" ]
 }