Add a RWH_TabSwitchPaintDuration histogram.

The RWH_TabSwitchPaintDuration histogram calculates
the amount of time it took after a particular view was
selected for it to be fully painted.

I modified the tab switching test to use the new tab
switch paint duration histogram in place of the whiteout
duration histogram.  As a measure, whiteout duration
would not carry a value if we kept the backing store
around for a tab, and we would end up with a result of
zero instead of a useful result.  Local results with the
new measure are consistent with the number of operations
we perform on the tabs.

The tab switching test now fails if it cannot locate
the correct histogram.

BUG=4104
TEST=count of tab switch paint duration histogram
results in tab switching test equals number of tabs
used in test

Review URL: http://codereview.chromium.org/378038

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@31632 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 21 insertions, 20 deletions

diff --git a/chrome/test/tab_switching/tab_switching_test.cc b/chrome/test/tab_switching/tab_switching_test.cc
index d23bef9..6b1eb00 100644
--- a/chrome/test/tab_switching/tab_switching_test.cc
+++ b/chrome/test/tab_switching/tab_switching_test.cc
@@ -25,7 +25,7 @@ namespace {
 // time taken for each switch. It then prints out the times on the console,
 // with the aim that the page cycler parser can interpret these numbers to
 // draw graphs for page cycler Tab Switching Performance.
-// Usage Flags: -enable-logging -dump-histograms-on-exit -log-level=0
+// Usage Flags: --enable-logging --dump-histograms-on-exit --log-level=0
 class TabSwitchingUITest : public UITest {
  public:
   TabSwitchingUITest() {
@@ -61,7 +61,7 @@ class TabSwitchingUITest : public UITest {
     EXPECT_TRUE(CloseBrowser(browser_proxy_.get(), &application_closed));
 
     // Now open the corresponding log file and collect average and std dev from
-    // the histogram stats generated for RenderWidgetHostHWND_WhiteoutDuration
+    // the histogram stats generated for RenderWidgetHost_TabSwitchPaintDuration
     FilePath log_file_name;
     ASSERT_TRUE(PathService::Get(chrome::DIR_LOGS, &log_file_name));
     log_file_name = log_file_name.AppendASCII("chrome_debug.log");
@@ -82,26 +82,27 @@ class TabSwitchingUITest : public UITest {
     const std::string average_str("average = ");
     const std::string std_dev_str("standard deviation = ");
     std::string::size_type pos = contents.find(
-        "Histogram: MPArch.RWHH_WhiteoutDuration", 0);
+        "Histogram: MPArch.RWH_TabSwitchPaintDuration", 0);
     std::string::size_type comma_pos;
     std::string::size_type number_length;
-    if (pos != std::string::npos) {
-      // Get the average.
-      pos = contents.find(average_str, pos);
-      comma_pos = contents.find(",", pos);
-      pos += average_str.length();
-      number_length = comma_pos - pos;
-      average = contents.substr(pos, number_length);
-
-      // Get the std dev.
-      pos = contents.find(std_dev_str, pos);
-      pos += std_dev_str.length();
-      comma_pos = contents.find(" ", pos);
-      number_length = comma_pos - pos;
-      std_dev = contents.substr(pos, number_length);
-    } else {
-      LOG(WARNING) << "Histogram: MPArch.RWHH_WhiteoutDuration wasn't found";
-    }
+
+    // Verify we found the TabSwitchPaintDuration histogram.
+    ASSERT_NE(pos, std::string::npos) <<
+        "Histogram: MPArch.RWH_TabSwitchPaintDuration wasn't found";
+
+    // Get the average.
+    pos = contents.find(average_str, pos);
+    comma_pos = contents.find(",", pos);
+    pos += average_str.length();
+    number_length = comma_pos - pos;
+    average = contents.substr(pos, number_length);
+
+    // Get the std dev.
+    pos = contents.find(std_dev_str, pos);
+    pos += std_dev_str.length();
+    comma_pos = contents.find(" ", pos);
+    number_length = comma_pos - pos;
+    std_dev = contents.substr(pos, number_length);
 
     // Print the average and standard deviation.
     PrintResultMeanAndError("tab_switch", "", "t",