Allow for pausing background tabs on desktop via about:flags.

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 22d3a66c2235d6fc4e31ca793faf991648ea670c..40f586297f5adaa2ff6693ca920302c91eea819b 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -100604,6 +100604,7 @@ from previous Chrome versions.
   <int value="-1772172557" label="enable-osk-overscroll"/>
   <int value="-1767470652" label="out-of-process-pdf"/>
   <int value="-1751928267" label="disable-icon-ntp"/>
+  <int value="-1749176684" label="PauseBackgroundTabs:disabled"/>
   <int value="-1746767834" label="ssl-interstitial-v2-gray"/>
   <int value="-1740519217" label="disable-software-rasterizer"/>
   <int value="-1735643253" label="enable-display-list-2d-canvas"/>
@@ -100631,6 +100632,7 @@ from previous Chrome versions.
   <int value="-1660972490" label="gpu-rasterization-msaa-sample-count"/>
   <int value="-1655535052" label="enable-pointer-events"/>
   <int value="-1654344175" label="disable-extension-info-dialog"/>
+  <int value="-1653838003" label="PauseBackgroundTabs:enabled"/>
   <int value="-1649778035" label="disable-clear-browsing-data-counters"/>
   <int value="-1648216169" label="NewOmniboxAnswerTypes:disabled"/>
   <int value="-1634154256" label="ZeroSuggestRedirectToChrome:enabled"/>