Rename source_prereqs to inputs in the GN build.

This variable changed name.

R=jamesr@chromium.org

Review URL: https://codereview.chromium.org/375873006

Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: a901cc9a31b96f16796290262cf248abb6432980
diff --git a/tools/gn/target_generator.cc b/tools/gn/target_generator.cc
index 084c587..252d982 100644
--- a/tools/gn/target_generator.cc
+++ b/tools/gn/target_generator.cc
@@ -163,10 +163,10 @@
 void TargetGenerator::FillInputs() {
   const Value* value = scope_->GetValue(variables::kInputs, true);
   if (!value) {
-    // Older versions used "source_prereqs". Allow use of this variable until
+    // Older versions used "inputs". Allow use of this variable until
     // all callers are updated.
     // TODO(brettw) remove this eventually.
-    value = scope_->GetValue("source_prereqs", true);
+    value = scope_->GetValue("inputs", true);
 
     if (!value)
       return;