[artifacts] Revert "Read gcs_bucket from output properties, not input"

This reverts commit 2e81ae1df391e7b90b9c38f4371330de2ac316c4.

Reason for revert: May be causing system OTA test to fail


Original change's description:
> [artifacts] Read gcs_bucket from output properties, not input
>
> This is better because:
> * It's much more intuitive that something outside a build depends on its
>   outputs rather than its inputs.
> * Our recipe code expects this. It's setting the output property
>   gcs_bucket already, not the input property.
>
> Change-Id: Id2ad57c08e4f60a7bd20310afabec9210ca7bffb

TBR=garymm@google.com,atyfto@google.com,kylecameron@google.com

Change-Id: Ic31c219907ec65a2adc2a5f011dd7c553a96481c
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
diff --git a/buildbucket/build.go b/buildbucket/build.go
index dfb9823..f7fce73 100644
--- a/buildbucket/build.go
+++ b/buildbucket/build.go
@@ -17,10 +17,10 @@
 	return b.Input.GitilesCommit
 }
 
-// OutputProperty returns the output property with the given name. Returns (nil, false)
-// if not found.
-func (b Build) OutputProperty(name string) (*Property, bool) {
-	prop, ok := b.Output.Properties.Fields[name]
+// Property reads a specific input Property from this builder. Returns false with a nil
+// Property if not found.
+func (b Build) Property(name string) (*Property, bool) {
+	prop, ok := b.Input.Properties.Fields[name]
 	if !ok {
 		return nil, false
 	}
diff --git a/cmd/artifacts/common.go b/cmd/artifacts/common.go
index 42ccd7b..e23c2b2 100644
--- a/cmd/artifacts/common.go
+++ b/cmd/artifacts/common.go
@@ -47,9 +47,9 @@
 	}
 
 	wrapper := buildbucket.Build(*response)
-	property, ok := wrapper.OutputProperty(bucketPropertyName)
+	property, ok := wrapper.Property(bucketPropertyName)
 	if !ok {
-		return "", fmt.Errorf("no output property %q found for build %q", bucketPropertyName, build)
+		return "", fmt.Errorf("no property %q found for build %q", bucketPropertyName, build)
 	}
 
 	return property.StringValue(), nil
diff --git a/cmd/artifacts/common_test.go b/cmd/artifacts/common_test.go
index b4df735..c23a3c4 100644
--- a/cmd/artifacts/common_test.go
+++ b/cmd/artifacts/common_test.go
@@ -50,7 +50,7 @@
 			mock: mockBuildsClient{
 				response: &buildbucketpb.Build{
 					Id: 123,
-					Output: &buildbucketpb.Build_Output{
+					Input: &buildbucketpb.Build_Input{
 						Properties: &_struct.Struct{
 							Fields: map[string]*_struct.Value{
 								"gcs_bucket": &_struct.Value{
@@ -90,7 +90,7 @@
 				shouldErr: true,
 				response: &buildbucketpb.Build{
 					Id: 123,
-					Output: &buildbucketpb.Build_Output{
+					Input: &buildbucketpb.Build_Input{
 						Properties: &_struct.Struct{
 							Fields: map[string]*_struct.Value{},
 						},
@@ -110,7 +110,7 @@
 			mock: mockBuildsClient{
 				response: &buildbucketpb.Build{
 					Id: 123,
-					Output: &buildbucketpb.Build_Output{
+					Input: &buildbucketpb.Build_Input{
 						Properties: &_struct.Struct{
 							Fields: map[string]*_struct.Value{},
 						},