Add support for .proto files in java modules

Test: m -j checkbuild
Change-Id: Ia03429948baebff85164a91a34507866c97a08ef

cc/gen.go

@@ -153,10 +153,9 @@ func genSources(ctx android.ModuleContext, srcFiles android.Paths,
 			srcFiles[i] = cppFile
 			genLex(ctx, srcFile, cppFile)
 		case ".proto":
-			protoFiles := android.GenProto(ctx, srcFile, buildFlags.protoFlags,
-				"--cpp_out", "", []string{"pb.cc", "pb.h"})
-			srcFiles[i] = protoFiles[0]
-			deps = append(deps, protoFiles[1])
+			ccFile, headerFile := genProto(ctx, srcFile, buildFlags.protoFlags)
+			srcFiles[i] = ccFile
+			deps = append(deps, headerFile)
 		case ".aidl":
 			cppFile := android.GenPathWithExt(ctx, "aidl", srcFile, "cpp")
 			srcFiles[i] = cppFile

cc/proto.go

@@ -15,11 +15,46 @@
 package cc
 
 import (
+	"github.com/google/blueprint"
 	"github.com/google/blueprint/proptools"
 
 	"android/soong/android"
 )
 
+func init() {
+	pctx.HostBinToolVariable("protocCmd", "aprotoc")
+}
+
+var (
+	proto = pctx.AndroidStaticRule("protoc",
+		blueprint.RuleParams{
+			Command:     "$protocCmd --cpp_out=$outDir $protoFlags $in",
+			CommandDeps: []string{"$protocCmd"},
+		}, "protoFlags", "outDir")
+)
+
+// genProto creates a rule to convert a .proto file to generated .pb.cc and .pb.h files and returns
+// the paths to the generated files.
+func genProto(ctx android.ModuleContext, protoFile android.Path,
+	protoFlags string) (ccFile, headerFile android.WritablePath) {
+
+	ccFile = android.GenPathWithExt(ctx, "proto", protoFile, "pb.cc")
+	headerFile = android.GenPathWithExt(ctx, "proto", protoFile, "pb.h")
+
+	ctx.ModuleBuild(pctx, android.ModuleBuildParams{
+		Rule:        proto,
+		Description: "protoc " + protoFile.Rel(),
+		Outputs:     android.WritablePaths{ccFile, headerFile},
+		Input:       protoFile,
+		Args: map[string]string{
+			"outDir":     android.ProtoDir(ctx).String(),
+			"protoFlags": protoFlags,
+		},
+	})
+
+	return ccFile, headerFile
+}
+
 func protoDeps(ctx BaseModuleContext, deps Deps, p *android.ProtoProperties, static bool) Deps {
 	var lib string