Add PeerConnectionInterface::UpdateCallBitrate with call tests.

webrtc/call/call.h

Index: webrtc/call/call.h
diff --git a/webrtc/call/call.h b/webrtc/call/call.h
index f67b6907e5f7a1c3465b984dc23de768f6130631..481f7086fd7fc93138dbb20361bb05a774414f47 100644
--- a/webrtc/call/call.h
+++ b/webrtc/call/call.h
@@ -14,6 +14,7 @@
 #include <string>
 #include <vector>
 
+#include "webrtc/api/rtcerror.h"
 #include "webrtc/base/networkroute.h"
 #include "webrtc/base/platform_file.h"
 #include "webrtc/base/socket.h"
@@ -75,6 +76,16 @@ class Call {
       int max_bitrate_bps = -1;
     } bitrate_config;
 
+    // TODO(zstein): The implementaiton doesn't treat BitrateConfigMask as a
+    // mask anymore. Come up with a better name.
+
+    // Assumes that 0 <= min <= start <= max holds for set parameters.
+    struct BitrateConfigMask {
+      rtc::Optional<int> min_bitrate_bps;
+      rtc::Optional<int> start_bitrate_bps;
+      rtc::Optional<int> max_bitrate_bps;
+    };
+
     // AudioState which is possibly shared between multiple calls.
     // TODO(solenberg): Change this to a shared_ptr once we can use C++11.
     rtc::scoped_refptr<AudioState> audio_state;
@@ -141,14 +152,21 @@ class Call {
   // pacing delay, etc.
   virtual Stats GetStats() const = 0;
 
-  // TODO(pbos): Like BitrateConfig above this is currently per-stream instead
-  // of maximum for entire Call. This should be fixed along with the above.
-  // Specifying a start bitrate (>0) will currently reset the current bitrate
-  // estimate. This is due to how the 'x-google-start-bitrate' flag is currently
+  // The greater min and smaller max set by this and SetBitrateConfigMask will
+  // be used. The latest non-negative start value from either call will be used.
+  // Specifying a start bitrate (>0) will reset the current bitrate estimate.
+  // This is due to how the 'x-google-start-bitrate' flag is currently
   // implemented.
   virtual void SetBitrateConfig(
       const Config::BitrateConfig& bitrate_config) = 0;
 
+  // The greater min and smaller max set by this and SetBitrateConfig will be
+  // used. The latest non-negative start value form either call will be used.
+  // Specifying a start bitrate will reset the current bitrate estimate.
+  // Assumes 0 <= min <= start <= max holds for set parameters.
+  virtual void SetBitrateConfigMask(
+      const Config::BitrateConfigMask& bitrate_mask) = 0;
+
   // TODO(skvlad): When the unbundled case with multiple streams for the same
   // media type going over different networks is supported, track the state
   // for each stream separately. Right now it's global per media type.