Log information for Mixed Builds modules.

Test: Output matches expected. https://paste.googleplex.com/5913495636803584?raw
Performance evaluated: https://docs.google.com/spreadsheets/d/1X7eOVBKEZUwUWl5i8CDfBo9yUeZrDPXWi2JYO4BEZt4/edit?resourcekey=0-co8crIFW9dpiedhCMkhAgw#gid=0

Change-Id: I88780c7cc52a189a72216c5e2e499c96574b3731

android/bazel.go

@@ -338,9 +338,19 @@ func shouldKeepExistingBuildFileForDir(allowlist bp2BuildConversionAllowlist, di
 	return false
 }
 
-// MixedBuildsEnabled checks that a module is ready to be replaced by a
+// MixedBuildsEnabled returns true if a module is ready to be replaced by a
+// converted or handcrafted Bazel target. As a side effect, calling this
+// method will also log whether this module is mixed build enabled for
+// metrics reporting.
+func MixedBuildsEnabled(ctx ModuleContext) bool {
+	mixedBuildEnabled := mixedBuildPossible(ctx)
+	ctx.Config().LogMixedBuild(ctx, mixedBuildEnabled)
+	return mixedBuildEnabled
+}
+
+// mixedBuildPossible returns true if a module is ready to be replaced by a
 // converted or handcrafted Bazel target.
-func (b *BazelModuleBase) MixedBuildsEnabled(ctx ModuleContext) bool {
+func mixedBuildPossible(ctx ModuleContext) bool {
 	if ctx.Os() == Windows {
 		// Windows toolchains are not currently supported.
 		return false