Fix image filters for PDF backend.

src/core/SkDevice.cpp

Index: src/core/SkDevice.cpp
diff --git a/src/core/SkDevice.cpp b/src/core/SkDevice.cpp
index 0623f9909e101361474668ab71e1e06a6edea426..b912e6aef0ca06f0b2511666781f40b39d8dc4e7 100644
--- a/src/core/SkDevice.cpp
+++ b/src/core/SkDevice.cpp
@@ -36,6 +36,10 @@ SkBaseDevice* SkBaseDevice::createCompatibleDeviceForSaveLayer(const SkImageInfo
     return this->onCreateDevice(info, kSaveLayer_Usage);
 }
 
+SkBaseDevice* SkBaseDevice::createCompatibleDeviceForImageFilter(const SkImageInfo& info) {
+    return this->onCreateDevice(info, kImageFilter_Usage);
+}
+
 SkMetaData& SkBaseDevice::getMetaData() {
     // metadata users are rare, so we lazily allocate it. If that changes we
     // can decide to just make it a field in the device (rather than a ptr)