Added UMA for usage of BudgetAPI calls.

chrome/browser/budget_service/budget_manager.cc

Index: chrome/browser/budget_service/budget_manager.cc
diff --git a/chrome/browser/budget_service/budget_manager.cc b/chrome/browser/budget_service/budget_manager.cc
index cdf4fd71c885c1600d30b938cd913f3f32728e69..a92c41f0a2e12a23ed8770f447abe4a2ccedbde0 100644
--- a/chrome/browser/budget_service/budget_manager.cc
+++ b/chrome/browser/budget_service/budget_manager.cc
@@ -74,7 +74,9 @@ void BudgetManager::GetBudget(const url::Origin& origin,
                  mojo::Array<blink::mojom::BudgetStatePtr>());
     return;
   }
-  db_.GetBudgetDetails(origin, callback);
+  db_.GetBudgetDetails(origin,
+                       base::Bind(&BudgetManager::DidGetBudget,
+                                  weak_ptr_factory_.GetWeakPtr(), callback));
 }
 
 void BudgetManager::Reserve(const url::Origin& origin,
@@ -122,6 +124,20 @@ void BudgetManager::Consume(const url::Origin& origin,
                              weak_ptr_factory_.GetWeakPtr(), callback));
 }
 
+void BudgetManager::DidGetBudget(
+    const GetBudgetCallback& callback,
+    const blink::mojom::BudgetServiceErrorType error,
+    mojo::Array<blink::mojom::BudgetStatePtr> budget) {
+  // If there was an error, just record a budget of 0, so the API query is still
+  // counted.
+  if (error != blink::mojom::BudgetServiceErrorType::NONE)
+    UMA_HISTOGRAM_COUNTS_100("BudgetAPI.QueryBudget", 0);
+  else
+    UMA_HISTOGRAM_COUNTS_100("BudgetAPI.QueryBudget", budget[0]->budget_at);

[Alexei Svitkine (slow), 2016/11/29 16:45:35]

Please refactor the code so the macro is only emitted once. Since each macro
expands to a bunch of code.

[harkness, 2016/11/30 11:31:52]

Done.

+
+  callback.Run(error, std::move(budget));
+}
+
 void BudgetManager::DidConsume(const ConsumeCallback& callback,
                                blink::mojom::BudgetServiceErrorType error,
                                bool success) {
@@ -142,5 +158,7 @@ void BudgetManager::DidReserve(const url::Origin& origin,
   if (success && error == blink::mojom::BudgetServiceErrorType::NONE)
     reservation_map_[origin]++;
 
+  UMA_HISTOGRAM_BOOLEAN("BudgetAPI.Reserve", success);
+
   callback.Run(error, success);
 }