--- a/dom/animation/KeyframeEffectReadOnly.h
+++ b/dom/animation/KeyframeEffectReadOnly.h
@@ -18,17 +18,17 @@
 #include "mozilla/AnimationTarget.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/ComputedTimingFunction.h"
 #include "mozilla/EffectCompositor.h"
 #include "mozilla/Keyframe.h"
 #include "mozilla/KeyframeEffectParams.h"
 // RawServoDeclarationBlock and associated RefPtrTraits
 #include "mozilla/ServoBindingTypes.h"
-#include "mozilla/StyleAnimationValueInlines.h"
+#include "mozilla/StyleAnimationValue.h"
 #include "mozilla/dom/AnimationEffectReadOnly.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/Element.h"
 
 struct JSContext;
 class JSObject;
 class nsIContent;
 class nsIDocument;

--- a/layout/base/nsLayoutUtils.cpp
+++ b/layout/base/nsLayoutUtils.cpp
@@ -112,17 +112,17 @@
 #include "nsFrameSelection.h"
 #include "FrameLayerBuilder.h"
 #include "mozilla/layers/APZCTreeManager.h"
 #include "mozilla/layers/CompositorBridgeChild.h"
 #include "mozilla/Telemetry.h"
 #include "mozilla/EventDispatcher.h"
 #include "mozilla/EventStateManager.h"
 #include "mozilla/RuleNodeCacheConditions.h"
-#include "mozilla/StyleAnimationValueInlines.h"
+#include "mozilla/StyleAnimationValue.h"
 #include "mozilla/StyleSetHandle.h"
 #include "mozilla/StyleSetHandleInlines.h"
 #include "RegionBuilder.h"
 #include "SVGSVGElement.h"
 
 #ifdef MOZ_XUL
 #include "nsXULPopupManager.h"
 #endif

--- a/layout/painting/nsDisplayList.cpp
+++ b/layout/painting/nsDisplayList.cpp
@@ -56,17 +56,18 @@
 #include "mozilla/AnimationUtils.h"
 #include "mozilla/EffectCompositor.h"
 #include "mozilla/EffectSet.h"
 #include "mozilla/EventStates.h"
 #include "mozilla/LookAndFeel.h"
 #include "mozilla/OperatorNewExtensions.h"
 #include "mozilla/PendingAnimationTracker.h"
 #include "mozilla/Preferences.h"
-#include "mozilla/StyleAnimationValueInlines.h"
+#include "mozilla/StyleAnimationValue.h"
+#include "mozilla/ServoBindings.h"
 #include "mozilla/Telemetry.h"
 #include "mozilla/UniquePtr.h"
 #include "mozilla/Unused.h"
 #include "mozilla/ViewportFrame.h"
 #include "mozilla/gfx/gfxVars.h"
 #include "ActiveLayerTracker.h"
 #include "nsContentUtils.h"
 #include "nsPrintfCString.h"

--- a/layout/style/StyleAnimationValue.cpp
+++ b/layout/style/StyleAnimationValue.cpp
@@ -6,16 +6,17 @@
 
 /* Utilities for animation of computed style values */
 
 #include "mozilla/StyleAnimationValue.h"
 
 #include "mozilla/ArrayUtils.h"
 #include "mozilla/MathAlgorithms.h"
 #include "mozilla/RuleNodeCacheConditions.h"
+#include "mozilla/ServoBindings.h"
 #include "mozilla/StyleSetHandle.h"
 #include "mozilla/StyleSetHandleInlines.h"
 #include "mozilla/Tuple.h"
 #include "mozilla/UniquePtr.h"
 #include "nsAutoPtr.h"
 #include "nsCOMArray.h"
 #include "nsIStyleRule.h"
 #include "mozilla/css/StyleRule.h"
@@ -5187,8 +5188,57 @@ StyleAnimationValue::operator==(const St
                         aOther.GetStringBufferValue()) == 0);
     case eUnit_ComplexColor:
       return *mValue.mComplexColor == *aOther.mValue.mComplexColor;
   }
 
   NS_NOTREACHED("incomplete case");
   return false;
 }
+
+// AnimationValue Implementation
+
+bool
+AnimationValue::operator==(const AnimationValue& aOther) const
+{
+  // It is possible to compare an empty AnimationValue with others, so both
+  // mServo and mGecko could be null while comparing.
+  MOZ_ASSERT(!mServo || mGecko.IsNull());
+  if (mServo) {
+    return Servo_AnimationValue_DeepEqual(mServo, aOther.mServo);
+  }
+  return mGecko == aOther.mGecko;
+}
+
+float
+AnimationValue::GetOpacity() const
+{
+  MOZ_ASSERT(!mServo != mGecko.IsNull());
+  return mServo ? Servo_AnimationValue_GetOpacity(mServo)
+                : mGecko.GetFloatValue();
+}
+
+gfxSize
+AnimationValue::GetScaleValue(const nsIFrame* aFrame) const
+{
+  MOZ_ASSERT(!mServo != mGecko.IsNull());
+  if (mServo) {
+    RefPtr<nsCSSValueSharedList> list;
+    Servo_AnimationValue_GetTransform(mServo, &list);
+    return nsStyleTransformMatrix::GetScaleValue(list, aFrame);
+  }
+  return mGecko.GetScaleValue(aFrame);
+}
+
+void
+AnimationValue::SerializeSpecifiedValue(nsCSSPropertyID aProperty,
+                                        nsAString& aString) const
+{
+  MOZ_ASSERT(!mServo != mGecko.IsNull());
+  if (mServo) {
+    Servo_AnimationValue_Serialize(mServo, aProperty, &aString);
+    return;
+  }
+
+  DebugOnly<bool> uncomputeResult =
+    StyleAnimationValue::UncomputeValue(aProperty, mGecko, aString);
+  MOZ_ASSERT(uncomputeResult, "failed to uncompute StyleAnimationValue");
+}

--- a/layout/style/StyleAnimationValue.h
+++ b/layout/style/StyleAnimationValue.h
@@ -565,32 +565,37 @@ private:
   }
   static bool IsStringUnit(Unit aUnit) {
     return aUnit == eUnit_UnparsedString;
   }
 };
 
 struct AnimationValue
 {
+  // mGecko and mServo are mutually exclusive: only one or the other should
+  // ever be set.
+  // FIXME: After obsoleting StyleAnimationValue, we should remove mGecko, and
+  // make AnimationValue a wrapper of RawServoAnimationValue to hide these
+  // FFIs.
   StyleAnimationValue mGecko;
   RefPtr<RawServoAnimationValue> mServo;
 
-  inline bool operator==(const AnimationValue& aOther) const;
+  bool operator==(const AnimationValue& aOther) const;
 
   bool IsNull() const { return mGecko.IsNull() && !mServo; }
 
-  inline float GetOpacity() const;
+  float GetOpacity() const;
 
   // Returns the scale for mGecko or mServo, which are calculated with
   // reference to aFrame.
-  inline gfxSize GetScaleValue(const nsIFrame* aFrame) const;
+  gfxSize GetScaleValue(const nsIFrame* aFrame) const;
 
   // Uncompute this AnimationValue and then serialize it.
-  inline void SerializeSpecifiedValue(nsCSSPropertyID aProperty,
-                                      nsAString& aString) const;
+  void SerializeSpecifiedValue(nsCSSPropertyID aProperty,
+                               nsAString& aString) const;
 };
 
 struct PropertyStyleAnimationValuePair
 {
   nsCSSPropertyID mProperty;
   AnimationValue mValue;
 };
 } // namespace mozilla

deleted file mode 100644
--- a/layout/style/StyleAnimationValueInlines.h
+++ /dev/null
@@ -1,58 +0,0 @@
-/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#ifndef mozilla_StyleAnimationValueInlines_h_
-#define mozilla_StyleAnimationValueInlines_h_
-
-#include "mozilla/StyleAnimationValue.h"
-#include "mozilla/ServoBindings.h"
-
-namespace mozilla {
-
-bool
-AnimationValue::operator==(const AnimationValue& aOther) const
-{
-    // mGecko and mServo are mutual exclusive, one of them must be null
-    if (mServo) {
-      return Servo_AnimationValue_DeepEqual(mServo, aOther.mServo);
-    }
-    return mGecko == aOther.mGecko;
-}
-
-float
-AnimationValue::GetOpacity() const
-{
-  return mServo ? Servo_AnimationValue_GetOpacity(mServo)
-                : mGecko.GetFloatValue();
-}
-
-gfxSize
-AnimationValue::GetScaleValue(const nsIFrame* aFrame) const
-{
-  if (mServo) {
-    RefPtr<nsCSSValueSharedList> list;
-    Servo_AnimationValue_GetTransform(mServo, &list);
-    return nsStyleTransformMatrix::GetScaleValue(list, aFrame);
-  }
-  return mGecko.GetScaleValue(aFrame);
-}
-
-void
-AnimationValue::SerializeSpecifiedValue(nsCSSPropertyID aProperty,
-                                        nsAString& aString) const
-{
-  if (mServo) {
-    Servo_AnimationValue_Serialize(mServo, aProperty, &aString);
-    return;
-  }
-
-  DebugOnly<bool> uncomputeResult =
-    StyleAnimationValue::UncomputeValue(aProperty, mGecko, aString);
-  MOZ_ASSERT(uncomputeResult, "failed to uncompute StyleAnimationValue");
-}
-
-} // namespace mozilla
-
-#endif // mozilla_StyleAnimationValueInlines_h_

--- a/layout/style/moz.build
+++ b/layout/style/moz.build
@@ -110,17 +110,16 @@ EXPORTS.mozilla += [
     'ServoSpecifiedValues.h',
     'ServoStyleRule.h',
     'ServoStyleSet.h',
     'ServoStyleSheet.h',
     'ServoTypes.h',
     'ServoUtils.h',
     'SheetType.h',
     'StyleAnimationValue.h',
-    'StyleAnimationValueInlines.h',
     'StyleBackendType.h',
     'StyleComplexColor.h',
     'StyleContextSource.h',
     'StyleSetHandle.h',
     'StyleSetHandleInlines.h',
     'StyleSheet.h',
     'StyleSheetInfo.h',
     'StyleSheetInlines.h',