Moved HistogramSnapshotManager::PrepareDeltas definition to .cc file.

This method used to be a template. But since it's not anymore, it doesn't need
to be defined in the header file anymore.

Change-Id: I5e3b769ff4e7fced01524ddb39bf163b8e82f66f
Reviewed-on: https://chromium-review.googlesource.com/892184
Commit-Queue: François Degros <fdegros@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#533094}

base/metrics/histogram_snapshot_manager.cc

@@ -43,6 +43,17 @@ HistogramSnapshotManager::HistogramSnapshotManager(
 
 HistogramSnapshotManager::~HistogramSnapshotManager() = default;
 
+void HistogramSnapshotManager::PrepareDeltas(
+    const std::vector<HistogramBase*>& histograms,
+    HistogramBase::Flags flags_to_set,
+    HistogramBase::Flags required_flags) {
+  for (HistogramBase* const histogram : histograms) {
+    histogram->SetFlags(flags_to_set);
+    if ((histogram->flags() & required_flags) == required_flags)
+      PrepareDelta(histogram);
+  }
+}
+
 void HistogramSnapshotManager::PrepareDelta(HistogramBase* histogram) {
   if (!histogram->ValidateHistogramContents(true, 0))
     return;

base/metrics/histogram_snapshot_manager.h

@@ -41,13 +41,7 @@ class BASE_EXPORT HistogramSnapshotManager final {
   // |Histogram::kNoFlags|.
   void PrepareDeltas(const std::vector<HistogramBase*>& histograms,
                      HistogramBase::Flags flags_to_set,
-                     HistogramBase::Flags required_flags) {
-    for (HistogramBase* const histogram : histograms) {
-      histogram->SetFlags(flags_to_set);
-      if ((histogram->flags() & required_flags) == required_flags)
-        PrepareDelta(histogram);
-    }
-  }
+                     HistogramBase::Flags required_flags);
 
   // When the collection is not so simple as can be done using a single
   // iterator, the steps can be performed separately. Call PerpareDelta()