diff --git a/image/Decoder.cpp b/image/Decoder.cpp
index 69bced776439..9bc5b7b3fcfc 100644
--- a/image/Decoder.cpp
+++ b/image/Decoder.cpp
@@ -453,7 +453,7 @@ Decoder::PostFrameStop(Opacity aFrameOpacity
   // here when the first frame is complete.
   if (!ShouldSendPartialInvalidations() && mFrameCount == 1) {
     mInvalidRect.UnionRect(mInvalidRect,
-                           gfx::IntRect(gfx::IntPoint(0, 0), GetSize()));
+                           IntRect(IntPoint(), Size()));
   }
 }
 
diff --git a/image/Decoder.h b/image/Decoder.h
index a38d7613c55b..38be32d0fa11 100644
--- a/image/Decoder.h
+++ b/image/Decoder.h
@@ -266,7 +266,7 @@ public:
    *
    * Illegal to call if HasSize() returns false.
    */
-  gfx::IntSize GetSize() const
+  gfx::IntSize Size() const
   {
     MOZ_ASSERT(HasSize());
     return mImageMetadata.GetSize();
@@ -282,7 +282,7 @@ public:
   gfx::IntSize OutputSize() const
   {
     return mDownscaler ? mDownscaler->TargetSize()
-                       : GetSize();
+                       : Size();
   }
 
   virtual Telemetry::ID SpeedHistogram();
@@ -411,8 +411,7 @@ protected:
 
   /// Helper method for decoders which only have 'basic' frame allocation needs.
   nsresult AllocateBasicFrame() {
-    nsIntSize size = GetSize();
-    return AllocateFrame(0, size, nsIntRect(nsIntPoint(), size),
+    return AllocateFrame(0, Size(), gfx::IntRect(gfx::IntPoint(), Size()),
                          gfx::SurfaceFormat::B8G8R8A8);
   }
 
diff --git a/image/decoders/nsBMPDecoder.cpp b/image/decoders/nsBMPDecoder.cpp
index e86c2ebe51fd..ec876c643660 100644
--- a/image/decoders/nsBMPDecoder.cpp
+++ b/image/decoders/nsBMPDecoder.cpp
@@ -686,7 +686,7 @@ nsBMPDecoder::ReadBitfields(const char* aData, size_t aLength)
     // BMPs store their rows in reverse order, so the downscaler needs to
     // reverse them again when writing its output. Unless the height is
     // negative!
-    rv = mDownscaler->BeginFrame(GetSize(), Nothing(),
+    rv = mDownscaler->BeginFrame(Size(), Nothing(),
                                  mImageData, mMayHaveTransparency,
                                  /* aFlipVertically = */ mH.mHeight >= 0);
     if (NS_FAILED(rv)) {
diff --git a/image/decoders/nsGIFDecoder2.cpp b/image/decoders/nsGIFDecoder2.cpp
index aaf4edd8e783..059d1e8102d8 100644
--- a/image/decoders/nsGIFDecoder2.cpp
+++ b/image/decoders/nsGIFDecoder2.cpp
@@ -199,7 +199,7 @@ nsGIFDecoder2::BeginImageFrame(const IntRect& aFrameRect,
     // The first frame is always decoded into an RGB surface.
     pipe =
       SurfacePipeFactory::CreateSurfacePipe(this, mGIFStruct.images_decoded,
-                                            GetSize(), OutputSize(),
+                                            Size(), OutputSize(),
                                             aFrameRect, format, pipeFlags);
   } else {
     // This is an animation frame (and not the first). To minimize the memory
@@ -207,7 +207,7 @@ nsGIFDecoder2::BeginImageFrame(const IntRect& aFrameRect,
     MOZ_ASSERT(!mDownscaler);
     pipe =
       SurfacePipeFactory::CreatePalettedSurfacePipe(this, mGIFStruct.images_decoded,
-                                                    GetSize(), aFrameRect, format,
+                                                    Size(), aFrameRect, format,
                                                     aDepth, pipeFlags);
   }
 
diff --git a/image/decoders/nsICODecoder.cpp b/image/decoders/nsICODecoder.cpp
index fcf2abdfc141..e2e097123f92 100644
--- a/image/decoders/nsICODecoder.cpp
+++ b/image/decoders/nsICODecoder.cpp
@@ -582,7 +582,7 @@ nsICODecoder::FinishResource()
   // Make sure the actual size of the resource matches the size in the directory
   // entry. If not, we consider the image corrupt.
   if (mContainedDecoder->HasSize() &&
-      mContainedDecoder->GetSize() != GetRealSize()) {
+      mContainedDecoder->Size() != GetRealSize()) {
     return Transition::TerminateFailure();
   }
 
diff --git a/image/decoders/nsIconDecoder.cpp b/image/decoders/nsIconDecoder.cpp
index e2929c8314d7..3a223e9dc62d 100644
--- a/image/decoders/nsIconDecoder.cpp
+++ b/image/decoders/nsIconDecoder.cpp
@@ -70,8 +70,8 @@ nsIconDecoder::ReadHeader(const char* aData)
 
   MOZ_ASSERT(!mImageData, "Already have a buffer allocated?");
   Maybe<SurfacePipe> pipe =
-    SurfacePipeFactory::CreateSurfacePipe(this, 0, GetSize(), OutputSize(),
-                                          IntRect(IntPoint(), GetSize()),
+    SurfacePipeFactory::CreateSurfacePipe(this, 0, Size(), OutputSize(),
+                                          IntRect(IntPoint(), Size()),
                                           SurfaceFormat::B8G8R8A8,
                                           SurfacePipeFlags());
   if (!pipe) {
diff --git a/image/decoders/nsJPEGDecoder.cpp b/image/decoders/nsJPEGDecoder.cpp
index afb6d769f4d4..fa3143a06c45 100644
--- a/image/decoders/nsJPEGDecoder.cpp
+++ b/image/decoders/nsJPEGDecoder.cpp
@@ -401,7 +401,7 @@ nsJPEGDecoder::ReadJPEGData(const char* aData, size_t aLength)
     MOZ_ASSERT(mImageData, "Should have a buffer now");
 
     if (mDownscaler) {
-      nsresult rv = mDownscaler->BeginFrame(GetSize(), Nothing(),
+      nsresult rv = mDownscaler->BeginFrame(Size(), Nothing(),
                                             mImageData,
                                             /* aHasAlpha = */ false);
       if (NS_FAILED(rv)) {
diff --git a/image/decoders/nsPNGDecoder.cpp b/image/decoders/nsPNGDecoder.cpp
index b9ce414a60e3..e8fb964f6861 100644
--- a/image/decoders/nsPNGDecoder.cpp
+++ b/image/decoders/nsPNGDecoder.cpp
@@ -151,7 +151,7 @@ nsPNGDecoder::GetTransparencyType(SurfaceFormat aFormat,
   if (aFormat == SurfaceFormat::B8G8R8A8) {
     return TransparencyType::eAlpha;
   }
-  if (!IntRect(IntPoint(), GetSize()).IsEqualEdges(aFrameRect)) {
+  if (!IntRect(IntPoint(), Size()).IsEqualEdges(aFrameRect)) {
     MOZ_ASSERT(HasAnimation());
     return TransparencyType::eFrameRect;
   }
@@ -213,7 +213,7 @@ nsPNGDecoder::CreateFrame(const FrameInfo& aFrameInfo)
   }
 
   Maybe<SurfacePipe> pipe =
-    SurfacePipeFactory::CreateSurfacePipe(this, mNumFrames, GetSize(),
+    SurfacePipeFactory::CreateSurfacePipe(this, mNumFrames, Size(),
                                           OutputSize(), aFrameInfo.mFrameRect,
                                           format, pipeFlags);
 
diff --git a/image/test/gtest/TestDecoders.cpp b/image/test/gtest/TestDecoders.cpp
index 94f4731347c9..e7fdfa76f2fe 100644
--- a/image/test/gtest/TestDecoders.cpp
+++ b/image/test/gtest/TestDecoders.cpp
@@ -55,7 +55,7 @@ CheckDecoderState(const ImageTestCase& aTestCase, Decoder* aDecoder)
             bool(progress & FLAG_IS_ANIMATED));
 
   // The decoder should get the correct size.
-  IntSize size = aDecoder->GetSize();
+  IntSize size = aDecoder->Size();
   EXPECT_EQ(aTestCase.mSize.width, size.width);
   EXPECT_EQ(aTestCase.mSize.height, size.height);
 
diff --git a/image/test/gtest/TestMetadata.cpp b/image/test/gtest/TestMetadata.cpp
index 722a16cd3bda..b86911b82d10 100644
--- a/image/test/gtest/TestMetadata.cpp
+++ b/image/test/gtest/TestMetadata.cpp
@@ -88,7 +88,7 @@ CheckMetadata(const ImageTestCase& aTestCase,
   // Check that we got the expected metadata.
   EXPECT_TRUE(metadataProgress & FLAG_SIZE_AVAILABLE);
 
-  IntSize metadataSize = decoder->GetSize();
+  IntSize metadataSize = decoder->Size();
   EXPECT_EQ(aTestCase.mSize.width, metadataSize.width);
   EXPECT_EQ(aTestCase.mSize.height, metadataSize.height);
 
@@ -122,7 +122,7 @@ CheckMetadata(const ImageTestCase& aTestCase,
   EXPECT_EQ(fullProgress, metadataProgress | fullProgress);
 
   // The full decoder and the metadata decoder should agree on the image's size.
-  IntSize fullSize = decoder->GetSize();
+  IntSize fullSize = decoder->Size();
   EXPECT_EQ(metadataSize.width, fullSize.width);
   EXPECT_EQ(metadataSize.height, fullSize.height);