Create a Lite Page bit for previews and fallback to Lo-Fi

components/data_reduction_proxy/core/common/data_reduction_proxy_params.cc

Index: components/data_reduction_proxy/core/common/data_reduction_proxy_params.cc
diff --git a/components/data_reduction_proxy/core/common/data_reduction_proxy_params.cc b/components/data_reduction_proxy/core/common/data_reduction_proxy_params.cc
index 52f7982699d94f57d7f0f2be4442aba806312e9a..ac08fb10e9dd25abf5e23f677714624275d659ce 100644
--- a/components/data_reduction_proxy/core/common/data_reduction_proxy_params.cc
+++ b/components/data_reduction_proxy/core/common/data_reduction_proxy_params.cc
@@ -41,6 +41,8 @@ const char kAndroidOneIdentifier[] = "sprout";
 const char kQuicFieldTrial[] = "DataReductionProxyUseQuic";
 
 const char kLoFiFieldTrial[] = "DataCompressionProxyLoFi";
+const char kLitePageFallbackFieldTrial[] =
+    "DataCompressionProxyLitePageFallback";
 const char kLoFiFlagFieldTrial[] = "DataCompressionProxyLoFiFlag";
 
 const char kTrustedSpdyProxyFieldTrialName[] = "DataReductionTrustedSpdyProxy";
@@ -104,6 +106,10 @@ const char* GetLoFiFieldTrialName() {
   return kLoFiFieldTrial;
 }
 
+const char* GetLitePageFallbackFieldTrialName() {
+  return kLitePageFallbackFieldTrial;
+}
+
 const char* GetLoFiFlagFieldTrialName() {
   return kLoFiFlagFieldTrial;
 }
@@ -125,6 +131,11 @@ bool IsIncludedInLitePageFieldTrial() {
                           kLitePage, base::CompareCase::SENSITIVE);
 }
 
+bool IsLitePageFallbackEnabled() {
+  return IsIncludedInFieldTrial(GetLitePageFallbackFieldTrialName()) ||
+         (IsLoFiOnViaFlags() && AreLitePagesEnabledViaFlags());
+}
+
 bool IsIncludedInServerExperimentsFieldTrial() {
   return !base::CommandLine::ForCurrentProcess()->HasSwitch(
              data_reduction_proxy::switches::