Clarify ExistentPathForSource docs

Specify that these paths are relative to SrcDir, not relative to a
module's local source directory.

Test: n/a
Change-Id: I9a80f19b2eb3a15e6276e98200796b0680af9ee7
diff --git a/android/paths.go b/android/paths.go
index 8106958..ada420d 100644
--- a/android/paths.go
+++ b/android/paths.go
@@ -279,7 +279,8 @@
 	return false
 }
 
-// PathsForSource returns Paths rooted from SrcDir
+// PathsForSource returns Paths rooted from SrcDir, *not* rooted from the module's local source
+// directory
 func PathsForSource(ctx PathContext, paths []string) Paths {
 	ret := make(Paths, len(paths))
 	for i, path := range paths {
@@ -288,9 +289,9 @@
 	return ret
 }
 
-// ExistentPathsForSources returns a list of Paths rooted from SrcDir that are
-// found in the tree. If any are not found, they are omitted from the list,
-// and dependencies are added so that we're re-run when they are added.
+// ExistentPathsForSources returns a list of Paths rooted from SrcDir, *not* rooted from the
+// module's local source directory, that are found in the tree. If any are not found, they are
+// omitted from the list, and dependencies are added so that we're re-run when they are added.
 func ExistentPathsForSources(ctx PathContext, paths []string) Paths {
 	ret := make(Paths, 0, len(paths))
 	for _, path := range paths {
@@ -914,9 +915,10 @@
 	return path
 }
 
-// ExistentPathForSource returns an OptionalPath with the SourcePath if the
-// path exists, or an empty OptionalPath if it doesn't exist. Dependencies are added
-// so that the ninja file will be regenerated if the state of the path changes.
+// ExistentPathForSource returns an OptionalPath with the SourcePath, rooted from SrcDir, *not*
+// rooted from the module's local source directory, if the path exists, or an empty OptionalPath if
+// it doesn't exist. Dependencies are added so that the ninja file will be regenerated if the state
+// of the path changes.
 func ExistentPathForSource(ctx PathContext, pathComponents ...string) OptionalPath {
 	path, err := pathForSource(ctx, pathComponents...)
 	if err != nil {