amalgamated C SDK: drop C++ implementation files unused by the C ABI

Source:    5,727,555 → 5,557,692 bytes  (-169,863 = -3.0%)
Binary:    6,049,608 → 5,904,712 bytes  (-O0, -141 KB)
Binary:    2,265,688 → 2,220,504 bytes  (-O2, -44 KB / -2.0%)
Compile:   9.7s → 9.5s (-O0); 31.0s → 30.1s (-O2)

Drop two groups of C++ source files that are part of the SDK's GN closure
but unreachable from the C ABI surface in include/perfetto/public/abi/.

src/tracing/BUILD.gn (gated under enable_perfetto_minimal_trace_protos):
  console_interceptor.cc       — pretty-printed console output for
                                 in-process trace readback. Public C++
                                 only (ConsoleInterceptor::Register);
                                 nothing in include/perfetto/public/
                                 references it.
  track_event_state_tracker.cc — helper for replaying TrackEvent state in
                                 a consumer; only used by
                                 console_interceptor.cc.
  track_event_legacy.cc        — implementation of LegacyTraceId::Write.
                                 The class is constructed only inside
                                 `#if PERFETTO_ENABLE_LEGACY_TRACE_EVENTS`
                                 blocks (off by default), so the .cc
                                 symbol is dead.

src/base/BUILD.gn:
  cpu_info.cc       — used only by profiling and system_info data sources.
  ctrl_c_handler.cc — used only by perfetto_cmd.
  getopt_compat.cc  — Windows getopt fallback used only by command-line
                      tools.
  subprocess.cc + posix/windows variants — used only by tests and host
                      tools (perfetto_cmd, kallsyms loader, etc.).

All audit checks: zero non-test #include sites under src/{shared_lib,
tracing,protozero,protovm,ipc,base}/ and include/perfetto/{public,
tracing,ext/tracing}/ (excluding the dropped files' own self-references).

Author: dreveman

src/base/BUILD.gn

@@ -35,13 +35,10 @@ perfetto_component("base") {
   sources = [
     "android_utils.cc",
     "base64.cc",
-    "cpu_info.cc",
     "crash_keys.cc",
-    "ctrl_c_handler.cc",
     "event_fd.cc",
     "file_utils.cc",
     "fixed_string_writer.cc",
-    "getopt_compat.cc",
     "intrusive_list.cc",
     "intrusive_tree.cc",
     "log_ring_buffer.h",
@@ -70,6 +67,17 @@ perfetto_component("base") {
     "weak_runner.cc",
   ]
 
+  # Sources only used by host tools (perfetto_cmd, trace_processor probes,
+  # tests). Not reachable from any SDK closure entry point — gated under the
+  # same C-SDK-minimal flag used to drop unused per-domain protos.
+  if (!enable_perfetto_minimal_trace_protos) {
+    sources += [
+      "cpu_info.cc",
+      "ctrl_c_handler.cc",
+      "getopt_compat.cc",
+    ]
+  }
+
   if (!is_nacl) {
     sources += [
       "lock_free_task_runner.cc",
@@ -78,7 +86,7 @@ perfetto_component("base") {
     ]
   }
 
-  if (_subprocess_supported) {
+  if (_subprocess_supported && !enable_perfetto_minimal_trace_protos) {
     sources += [
       "subprocess.cc",
       "subprocess_posix.cc",

src/tracing/BUILD.gn

@@ -84,7 +84,6 @@ source_set("client_api_without_backends") {
     "../../include/perfetto/tracing",
   ]
   sources = [
-    "console_interceptor.cc",
     "data_source.cc",
     "debug_annotation.cc",
     "event_context.cc",
@@ -106,10 +105,30 @@ source_set("client_api_without_backends") {
     "tracing_policy.cc",
     "track.cc",
     "track_event_category_registry.cc",
-    "track_event_legacy.cc",
-    "track_event_state_tracker.cc",
     "virtual_destructors.cc",
   ]
+
+  # Optional C++-only SDK features that the C ABI doesn't expose:
+  #   - console_interceptor: pretty-printed text output for in-process trace
+  #     readback. Only used by C++ embedders calling
+  #     ConsoleInterceptor::Register; not surfaced via include/perfetto/public.
+  #   - track_event_state_tracker: helper for replaying TrackEvent state in a
+  #     consumer; only used by console_interceptor.
+  #   - track_event_legacy: implementation of LegacyTraceId::Write for the
+  #     PERFETTO_ENABLE_LEGACY_TRACE_EVENTS Chrome-style macros, off by
+  #     default. The internal::LegacyTraceId class is only constructed inside
+  #     `#if PERFETTO_ENABLE_LEGACY_TRACE_EVENTS` blocks in
+  #     internal/track_event_data_source.h, so the .cc symbol is never called
+  #     when the macro is off.
+  if (enable_perfetto_minimal_trace_protos) {
+    # Drop ~830 lines of C++ that the C SDK never reaches.
+  } else {
+    sources += [
+      "console_interceptor.cc",
+      "track_event_legacy.cc",
+      "track_event_state_tracker.cc",
+    ]
+  }
   assert_no_deps = [ "service" ]
   if (enable_perfetto_ipc) {
     assert_no_deps += [