Add srcDir to SourcePath

Bug: 183650682
Test: m droid
Change-Id: I08f7dba449538d289a6c4d6b5325c1a833cff834
diff --git a/android/paths.go b/android/paths.go
index 0ed988a..3a3643c 100644
--- a/android/paths.go
+++ b/android/paths.go
@@ -968,6 +968,9 @@
 // SourcePath is a Path representing a file path rooted from SrcDir
 type SourcePath struct {
 	basePath
+
+	// The sources root, i.e. Config.SrcDir()
+	srcDir string
 }
 
 var _ Path = SourcePath{}
@@ -981,7 +984,7 @@
 // code that is embedding ninja variables in paths
 func safePathForSource(ctx PathContext, pathComponents ...string) (SourcePath, error) {
 	p, err := validateSafePath(pathComponents...)
-	ret := SourcePath{basePath{p, ctx.Config(), ""}}
+	ret := SourcePath{basePath{p, ctx.Config(), ""}, ctx.Config().srcDir}
 	if err != nil {
 		return ret, err
 	}
@@ -997,7 +1000,7 @@
 // pathForSource creates a SourcePath from pathComponents, but does not check that it exists.
 func pathForSource(ctx PathContext, pathComponents ...string) (SourcePath, error) {
 	p, err := validatePath(pathComponents...)
-	ret := SourcePath{basePath{p, ctx.Config(), ""}}
+	ret := SourcePath{basePath{p, ctx.Config(), ""}, ctx.Config().srcDir}
 	if err != nil {
 		return ret, err
 	}
@@ -1091,7 +1094,7 @@
 }
 
 func (p SourcePath) String() string {
-	return filepath.Join(p.config.srcDir, p.path)
+	return filepath.Join(p.srcDir, p.path)
 }
 
 // Join creates a new SourcePath with paths... joined with the current path. The
@@ -1123,7 +1126,7 @@
 		ReportPathErrorf(ctx, "Cannot find relative path for %s(%s)", reflect.TypeOf(path).Name(), path)
 		return OptionalPath{}
 	}
-	dir := filepath.Join(p.config.srcDir, p.path, relDir)
+	dir := filepath.Join(p.srcDir, p.path, relDir)
 	// Use Glob so that we are run again if the directory is added.
 	if pathtools.IsGlob(dir) {
 		ReportPathErrorf(ctx, "Path may not contain a glob: %s", dir)
@@ -1136,7 +1139,7 @@
 	if len(paths) == 0 {
 		return OptionalPath{}
 	}
-	relPath := Rel(ctx, p.config.srcDir, paths[0])
+	relPath := Rel(ctx, p.srcDir, paths[0])
 	return OptionalPathForPath(PathForSource(ctx, relPath))
 }