Mark camera prims as varying if any attributes on the camera have time

samples. This matches the behavior of the light adapter, and handles extra
attributes added through API schemas applied to the camera.

pxr/usdImaging/usdImaging/cameraAdapter.cpp

@@ -194,6 +194,25 @@ UsdImagingCameraAdapter::TrackVariability(UsdPrim const& prim,
                 false);
         }
     }
+
+    if ((*timeVaryingBits & HdCamera::DirtyParams) != 0)
+        return;
+
+    // The block of code below was copied from `lightAdapter.cpp`
+    // If any of the camera attributes is time varying
+    // we will assume all camera params are time-varying.
+    const std::vector<UsdAttribute> &attrs = prim.GetAttributes();
+    for (UsdAttribute const& attr : attrs) {
+        // Don't double-count transform attrs.
+        if (UsdGeomXformable::IsTransformationAffectedByAttrNamed(
+                    attr.GetBaseName())) {
+            continue;
+        }
+        if (attr.GetNumTimeSamples()>1){
+            *timeVaryingBits |= HdCamera::DirtyParams;
+            break;
+        }
+    }
 }
 
 void