Remove the majority of the high-traffic Net.AsyncResourceHandler histograms.

Specifically:
Net.AsyncResourceHandler_PendingDataCount
Net.AsyncResourceHandler_PendingDataCount_WhenFull
Net.AsyncResourceHandler_SharedIOBuffer_Alloc
Net.AsyncResourceHandler_SharedIOBuffer_Used
Net.AsyncResourceHandler_SharedIOBuffer_UsedPercentage

Are any of these still looked at? They are still all unowned.

I've left Net.AsyncResourceHandler_RedirectHopTime since that is specifically owned by bnc@. Is this histogram still useful?

BUG=469288

Review URL: https://codereview.chromium.org/1025813002

Cr-Commit-Position: refs/heads/master@{#322011}

content/browser/loader/async_resource_handler.cc

@@ -12,7 +12,7 @@
 #include "base/debug/alias.h"
 #include "base/logging.h"
 #include "base/memory/shared_memory.h"
-#include "base/metrics/histogram.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/time/time.h"
 #include "content/browser/devtools/devtools_netlog_observer.h"
@@ -59,11 +59,6 @@ void InitializeResourceBufferConstants() {
   GetNumericArg("resource-buffer-max-allocation-size", &kMaxAllocationSize);
 }
 
-int CalcUsedPercentage(int bytes_read, int buffer_size) {
-  double ratio = static_cast<double>(bytes_read) / buffer_size;
-  return static_cast<int>(ratio * 100.0 + 0.5);  // Round to nearest integer.
-}
-
 }  // namespace
 
 class DependentIOBuffer : public net::WrappedIOBuffer {
@@ -256,9 +251,6 @@ bool AsyncResourceHandler::OnWillRead(scoped_refptr<net::IOBuffer>* buf,
   *buf = new DependentIOBuffer(buffer_.get(), memory);
   *buf_size = allocation_size_;
 
-  UMA_HISTOGRAM_CUSTOM_COUNTS(
-      "Net.AsyncResourceHandler_SharedIOBuffer_Alloc",
-      *buf_size, 0, kMaxAllocationSize, 100);
   return true;
 }
 
@@ -274,13 +266,6 @@ bool AsyncResourceHandler::OnReadCompleted(int bytes_read, bool* defer) {
 
   buffer_->ShrinkLastAllocation(bytes_read);
 
-  UMA_HISTOGRAM_CUSTOM_COUNTS(
-      "Net.AsyncResourceHandler_SharedIOBuffer_Used",
-      bytes_read, 0, kMaxAllocationSize, 100);
-  UMA_HISTOGRAM_PERCENTAGE(
-      "Net.AsyncResourceHandler_SharedIOBuffer_UsedPercentage",
-      CalcUsedPercentage(bytes_read, allocation_size_));
-
   if (!sent_first_data_msg_) {
     base::SharedMemoryHandle handle;
     int size;
@@ -300,14 +285,8 @@ bool AsyncResourceHandler::OnReadCompleted(int bytes_read, bool* defer) {
   filter->Send(new ResourceMsg_DataReceived(
       GetRequestID(), data_offset, bytes_read, encoded_data_length));
   ++pending_data_count_;
-  UMA_HISTOGRAM_CUSTOM_COUNTS(
-      "Net.AsyncResourceHandler_PendingDataCount",
-      pending_data_count_, 0, 100, 100);
 
   if (!buffer_->CanAllocate()) {
-    UMA_HISTOGRAM_CUSTOM_COUNTS(
-        "Net.AsyncResourceHandler_PendingDataCount_WhenFull",
-        pending_data_count_, 0, 100, 100);
     *defer = did_defer_ = true;
     OnDefer();
   }

tools/metrics/histograms/histograms.xml

@@ -16565,6 +16565,9 @@ Therefore, the affected-histogram name has to have at least one dot in it.
 </histogram>
 
 <histogram name="Net.AsyncResourceHandler_PendingDataCount">
+  <obsolete>
+    Deprecated 03/2015.
+  </obsolete>
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <summary>
     The count of unacknowledged ResourceMsg_DataReceived messages.  This message
@@ -16573,6 +16576,9 @@ Therefore, the affected-histogram name has to have at least one dot in it.
 </histogram>
 
 <histogram name="Net.AsyncResourceHandler_PendingDataCount_WhenFull">
+  <obsolete>
+    Deprecated 03/2015.
+  </obsolete>
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <summary>
     The count of unacknowledged ResourceMsg_DataReceived messages at the point
@@ -16590,17 +16596,26 @@ Therefore, the affected-histogram name has to have at least one dot in it.
 </histogram>
 
 <histogram name="Net.AsyncResourceHandler_SharedIOBuffer_Alloc" units="bytes">
+  <obsolete>
+    Deprecated 03/2015.
+  </obsolete>
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <summary>The size of a SharedIOBuffer allocation.</summary>
 </histogram>
 
 <histogram name="Net.AsyncResourceHandler_SharedIOBuffer_Used" units="bytes">
+  <obsolete>
+    Deprecated 03/2015.
+  </obsolete>
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <summary>The number of bytes copied into a SharedIOBuffer.</summary>
 </histogram>
 
 <histogram name="Net.AsyncResourceHandler_SharedIOBuffer_UsedPercentage"
     units="percentage">
+  <obsolete>
+    Deprecated 03/2015.
+  </obsolete>
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <summary>
     The percentage of a SharedIOBuffer allocation that is actually used.