Expand the functionality of the BudgetDatabase.

chrome/browser/budget_service/budget.proto

Index: chrome/browser/budget_service/budget.proto
diff --git a/chrome/browser/budget_service/budget.proto b/chrome/browser/budget_service/budget.proto
index 7e727936e03116e278342672f7d7cae5cec6b6f9..a21455382d85953939ff6abdcc5f45bcd17f1f8d 100644
--- a/chrome/browser/budget_service/budget.proto
+++ b/chrome/browser/budget_service/budget.proto
@@ -22,9 +22,9 @@ message Budget {
 // Next available id: 3
 message BudgetChunk {
   // The amount of budget remaining in this chunk.
-  optional double budget_amount = 1;
+  optional double amount = 1;
 
   // The timestamp when the budget expires. Format is double to integrate with
   // Site Engagement and Blink and is the number of seconds since Jan 1, 1970.
-  optional double expiration_timestamp = 2;
+  optional double expiration = 2;
 }