trace_processor: implement first android mem metric!

We fill the LMK field for now: more metrics will be filled in following
CLs.

Context: go/perfetto-metrics
Bug: 129747127
Change-Id: If3d7de375e16bbfd15a8b19bda05d3162ae30308
diff --git a/protos/BUILD b/protos/BUILD
index b41edf1..ed2ce1f 100644
--- a/protos/BUILD
+++ b/protos/BUILD
@@ -170,6 +170,45 @@
     ],
 )
 
+# GN target: //protos/perfetto/metrics/android:zero_gen
+proto_library(
+    name = "metrics_android_zero",
+    srcs = [
+        "perfetto/metrics/android/mem_metric.proto",
+    ],
+)
+
+# GN target: //protos/perfetto/metrics/android:zero_gen
+pbzero_cc_proto_library(
+    name = "metrics_android_zero_cc_proto",
+    src_proto_library = "//third_party/perfetto/protos:metrics_android_zero",
+    deps = [
+        "//third_party/perfetto:libprotozero",
+        "//third_party/perfetto/google:gtest_prod",
+    ],
+)
+
+# GN target: //protos/perfetto/metrics:zero_gen
+proto_library(
+    name = "metrics_zero",
+    srcs = [
+        "perfetto/metrics/metrics.proto",
+    ],
+    deps = [
+        "//third_party/perfetto/protos:metrics_android_zero",
+    ],
+)
+
+# GN target: //protos/perfetto/metrics:zero_gen
+pbzero_cc_proto_library(
+    name = "metrics_zero_cc_proto",
+    src_proto_library = "//third_party/perfetto/protos:metrics_zero",
+    deps = [
+        "//third_party/perfetto:libprotozero",
+        "//third_party/perfetto/google:gtest_prod",
+    ],
+)
+
 # GN target: //protos/third_party/pprof:lite_gen
 proto_library(
     name = "protos_third_party_pprof",