Revert "[rust bmp] Add UMA for tracking BMP `CompressionType`." This reverts commit b44e609869029819e871a5464dd2c2b542bde9da, because at this point we have gathered all the UMA data that was needed. OBSOLETE_HISTOGRAMS=Removed after required data has been gathered - see https://crbug.com/452667935#comment12 Fixed: 452667935 Change-Id: I85739a19b3672f253d77bed113c21e6e0a88e5da Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7253440 Reviewed-by: Daniel Cheng <dcheng@chromium.org> Commit-Queue: Nicolás Peña <npm@chromium.org> Auto-Submit: Łukasz Anforowicz <lukasza@chromium.org> Reviewed-by: Nicolás Peña <npm@chromium.org> Cr-Commit-Position: refs/heads/main@{#1558307}

diff --git a/third_party/blink/renderer/platform/image-decoders/bmp/bmp_image_reader.cc b/third_party/blink/renderer/platform/image-decoders/bmp/bmp_image_reader.cc
index 1d749c9..74a6e20 100644
--- a/third_party/blink/renderer/platform/image-decoders/bmp/bmp_image_reader.cc
+++ b/third_party/blink/renderer/platform/image-decoders/bmp/bmp_image_reader.cc

@@ -8,7 +8,6 @@
 
 #include "base/compiler_specific.h"
 #include "base/containers/span.h"
-#include "base/metrics/histogram_functions.h"
 #include "third_party/blink/renderer/platform/image-decoders/jpeg/jpeg_image_decoder.h"
 #include "third_party/blink/renderer/platform/image-decoders/png/png_image_decoder.h"
 #include "third_party/skia/include/core/SkColorSpace.h"
@@ -88,11 +87,6 @@
     return false;
   }
 
-  // TODO(https://crbug.com/452667935): Clean this up once we have sufficient
-  // data (when M143 or M144 reach Stable?).
-  base::UmaHistogramEnumeration("Blink.DecodedImage.BMP.CompressionType",
-                                info_header_.compression);
-
   // If there is an applicable color profile, it must be processed now, since
   // once the image size is available, the decoding machinery assumes the color
   // space is as well.  Unfortunately, since the profile appears after

diff --git a/third_party/blink/renderer/platform/image-decoders/bmp/bmp_image_reader.h b/third_party/blink/renderer/platform/image-decoders/bmp/bmp_image_reader.h
index cf1d133..f6c2118 100644
--- a/third_party/blink/renderer/platform/image-decoders/bmp/bmp_image_reader.h
+++ b/third_party/blink/renderer/platform/image-decoders/bmp/bmp_image_reader.h

@@ -66,17 +66,6 @@
 
   // The various BMP compression types.  We don't currently decode all
   // these.
-  //
-  // Corresponding specs:
-  //
-  // * https://learn.microsoft.com/en-us/previous-versions/dd183376(v=vs.85)
-  //   (search for `biCompression` - defines `BI_RGB`, `BI_RLE8`, `BI_RLE4`,
-  //   `BI_BITFIELDS`, `BI_JPEG`, and `BI_PNG`.
-  // * https://learn.microsoft.com/en-us/previous-versions/windows/embedded/aa452885(v=msdn.10)
-  //   (search for `biCompression` - defines `BI_RGB`, `BI_BITFIELDS`, and
-  //   `BI_ALPHABITFIELDS`)
-  //
-  // LINT.IfChange(CompressionType)
   enum CompressionType {
     // Universal types
     RGB = 0,
@@ -90,11 +79,7 @@
     // OS/2 2.x-only
     HUFFMAN1D,  // Stored in file as 3
     RLE24,      // Stored in file as 4
-
-    // `kMaxValue` is needed to support `base::UmaHistogramEnumeration`:
-    kMaxValue = RLE24,
   };
-  // LINT.ThenChange(//tools/metrics/histograms/metadata/blink/enums.xml:BmpCompressionType)
   enum ProcessingResult {
     kSuccess,
     kFailure,

diff --git a/tools/metrics/histograms/metadata/blink/enums.xml b/tools/metrics/histograms/metadata/blink/enums.xml
index 6e25ec1..9f2fc69 100644
--- a/tools/metrics/histograms/metadata/blink/enums.xml
+++ b/tools/metrics/histograms/metadata/blink/enums.xml

@@ -35,22 +35,6 @@
   <int value="5" label="Unsupported request from prefetch only document"/>
 </enum>
 
-<enum name="BmpCompressionType">
-<!-- LINT.IfChange(BmpCompressionType) -->
-
-  <int value="0" label="RGB"/>
-  <int value="1" label="RLE8"/>
-  <int value="2" label="RLE4"/>
-  <int value="3" label="BITFIELDS"/>
-  <int value="4" label="JPEG"/>
-  <int value="5" label="PNG"/>
-  <int value="6" label="ALPHABITFIELDS"/>
-  <int value="7" label="HUFFMAN1D"/>
-  <int value="8" label="RLE24"/>
-<!-- LINT.ThenChange(//third_party/blink/renderer/platform/image-decoders/bmp/bmp_image_reader.h:CompressionType) -->
-
-</enum>
-
 <enum name="BooleanContentChangeMode">
   <int value="0" label="Discard Content"/>
   <int value="1" label="Retain Content"/>

diff --git a/tools/metrics/histograms/metadata/blink/histograms.xml b/tools/metrics/histograms/metadata/blink/histograms.xml
index 3ae5a7df..2b97ac85 100644
--- a/tools/metrics/histograms/metadata/blink/histograms.xml
+++ b/tools/metrics/histograms/metadata/blink/histograms.xml

@@ -1009,18 +1009,6 @@
   </summary>
 </histogram>
 
-<histogram name="Blink.DecodedImage.BMP.CompressionType"
-    enum="BmpCompressionType" expires_after="2026-03-22">
-  <owner>lukasza@chromium.org</owner>
-  <owner>dcheng@chromium.org</owner>
-  <owner>kjlubick@chromium.org</owner>
-  <summary>
-    BMP compression type as seen by `blink::BMPImageReader::DecodeBMP` when a
-    BMP image is decoded (typically when rendering an image from the web, but
-    Blink decoders are also used in other code).
-  </summary>
-</histogram>
-
 <histogram name="Blink.DecodedImage.JpegDensity.Count.{ImageArea}"
     units="0.01 bits per pixel" expires_after="2026-04-26">
   <owner>wtc@google.com</owner>